arc spectrum experiment

PhysicsOpenLab Modern DIY Physics Laboratory for Science Enthusiasts

Arc atomic emission spectroscopy.

September 25, 2022 English Posts , Light , Spectrometer 5,530 Views

Abstract: in this article we describe the construction of a simple apparatus for spectroscopic analysis of atomic light emission from electric arc. The apparatus is based on a high voltage generator that produces an electric arc whose light emission is analyzed by a fiber optic spectrometer.

Introduction

Atomic Emission Spectroscopy (AES) is a chemical analysis method that uses the intensity of light emitted by a flame, plasma, arc, or spark at a particular wavelength to determine the amount of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum provides the identity of the element while the intensity of the light emitted is proportional to the quantity of the element.

Spark or arc atomic emission spectroscopy is used for the analysis of metallic elements in solid samples. For non-conductive materials, the sample is ground with graphite powder to make it conductive. In traditional arc spectroscopy methods, a sample of the solid is commonly ground and destroyed during analysis. An electric arc or spark is passed through the sample, heating it to a high temperature to excite the atoms within it. The excited atoms emit light at characteristic wavelengths which are analyzed by a spectrometer. Modern spark and arc sources with controlled discharges can also be used for quantitative analyzes, but with our DIY apparatus we will be satisfied with qualitative analyzes.

Experimental Setup

The experimental setup consists of a microscope stand (from China) made of aluminum and adjustable in height, it is quite robust and above all cheap, it is easily found on eCommerce sites by searching for “microscope stand”. On the base we fixed a Plexiglas plate and on the height-adjustable support we placed a cylinder, also in Plexiglas. We need these materials to electrically isolate our “stand” from the electrodes that will be polarized with the high voltage necessary to create the spark or the electric arc. On the Plexiglas base we placed an aluminum plate, connected to the high voltage GND cable, while on the Plexiglas cylinder we inserted a graphite electrode connected to the active high voltage cable. This setup is shown in Figure 1.

In figure 2 we show the complete apparatus with the electrode support, the positioning system for the optical fiber and the HV generator made with a flyback transformer driven by a royer oscillator. Our HV generator produces a high frequency alternating voltage so the electrodes are alternatively cathode and anode. It is obviously possible, and perhaps even preferable, to opt for a continuous HV voltage, in this last case the electric arc will have a constant polarization.

The plasma produces light emission due to the ionization of the gases and materials present in the arc production area. Generally speaking, emissions due to nitrogen and oxygen present in the air will always be present, we will also have emissions due to the material of the electrodes, in our case of graphite (carbon), there may also be light emissions due to contaminants, such as the ubiquitous sodium line at 589 nm. The material whose light emission is to be analyzed is positioned on the aluminum plate below the graphite electrode. If the material is a conductor, for example a metal, its vaporization by the plasma effect is usually sufficient to produce the characteristic light emission, especially if the metal has a low melting point. Alternatively, it is also possible to place on the aluminum plate some salts, in granular form or dissolved in aqueous solution. Also in this case the heat of the plasma vaporizes the sample which is ionized and produces the characteristic spectrum.

Measures of Spectra

The first spectrum acquired was that of the arc produced between two graphite electrodes, shown in figure 3. The peaks in this spectrum correspond to the emissions of oxygen and nitrogen gases and the carbon of the electrodes, there is also the sodium line, present as a contaminant. This spectrum will be considered as a reference for subsequent analyzes.

In figure 4 we report the spectrum of the arc obtained with a solution of strontium salts. The main emission line of strontium is clearly seen, together with the sodium contamination line.

In figure 5 we report the arc spectrum obtained with a solution of indium salts. The main emission line of the indium is clearly seen.

In figure 6 we report the arc spectrum obtained with a graphite and a lead electrode. Lead has a low melting point so it produces a fairly evident emission around 400 nm.

In figure 7 we report the arc spectrum obtained with a graphite and a magnesium electrode. Several characteristic emission lines are obtained.

For the copper emission analysis we used a copper sulphate solution, shown in the image below. The solution is poured onto the aluminum plate and the action of the electric arc produces its vaporization, bringing copper ions into the plasma that produce the emission lines shown in the spectrum in figure 8.

Conclusions

Our apparatus for the analysis of atomic light emission spectra generated by a plasma state produced by an electric arc or spark has allowed us to acquire some interesting spectra with the evidence of the characteristic emission lines. The quality of the spectrum obtained depends greatly on the degree of contamination of the samples and electrodes. Better results could be obtained in an inert atmosphere, for example with a flow of argon gas on the sample being analyzed. We have also noticed that the correct positioning of the optical fiber is very important, as it must “point” to the area of ​​the electric arc closest to the sample under examination. With a little patience and with the optimal choice of the sample, our apparatus also allows us to obtain good quality spectra that can be used for the qualitative analysis of the sample.

If you liked this post you can share it on the “social” Facebook , Twitter or LinkedIn with the buttons below. This way you can help us! Thank you !

If you like this site and if you want to contribute to the development of the activities you can make a donation, thank you !

Tags Spark spectroscopy

Gamma Spectroscopy with KC761B

Abstract: in this article, we continue the presentation of the new KC761B device. In the previous post, we described the apparatus in general terms. Now we mainly focus on the gamma spectrometer functionality.

'Refraction is then all there is to it': How Isaac Newton's experiments revealed the mystery of light

"The colors of the spectrum, then, "are not Qualifications [alterations] of Light … (as 'tis generally believed), but Original and connate properties."

The beauty and majesty of rainbows have inspired awe in humans for millennia, but it wasn't until Isaac Newton's groundbreaking work unlocking the secrets of light did we truly begin to understand how they form.

In this extract from the new book " Beautiful Experiments: An Illustrated History of Experimental Science " (The University of Chicago Press, 2023), science writer Philip Ball explains how Isaac Newton's ingenious experiment with prisms transformed our understanding of light.

The puzzle of the rainbow was resolved in the seventeenth century through the work of the scientist who some regard as the greatest ever to have lived. In 1666, Isaac Newton — then a 23-year-old Cambridge graduate — performed an experiment with light that transformed our understanding of it. 

While it was thought that the bar of rainbow colors — called a spectrum — produced when white light (like sunlight) travels through a glass prism is caused by some property of the prism that alters the light, Newton showed the colors are already inherent in the light itself. Legend has it that Newton did the experiment at his family home in Woolsthorpe, Lincolnshire, to which he had returned to escape the Great Plague that ravaged England in 1665. 

It did not, after all, require any fancy apparatus — just a few prisms, which could be bought almost as trinkets at markets (although he needed good-quality ones!). While there's truth in that, Newton had been planning such experiments for a while in his Cambridge room: we need not credit the plague for stimulating this leap in understanding optics. Newton didn't report his results until six years later, when he sent an account to the Royal Society in London, the intellectual center of "experimental philosophy" in the mid-century. 

Related: 9 equations that changed the world

He was famously reluctant to disclose the outcomes of his studies, and had to be cajoled into writing down his celebrated laws of motion and theories about the motions of the planets in his masterwork the Principia Mathematica in 1687. The book in which he recorded his experiments and theories about light, Opticks, was finally published in 1704. This was not so much because Newton was diffident about his work; on the contrary, he was rather covetous about it, and highly sensitive to criticism. 

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Newton begins his 1672 account by relating his surprise that the colored spectrum produced by his prism was rectangular in shape rather than circular, "as the received laws of Refraction" would lead one to expect. It seems a rather trifling question, especially to lead to such profound conclusions. In fact, his "surprise" is hard to credit, for this effect of a prism was well known, not least to Newton himself, who had been fascinated with such instruments since he was a boy. 

Newton was here no doubt indulging what is now a common practice in scientific papers: to construct a retrospective story so as to give a comprehensible narrative arc to a description of experiments that might have a more haphazard genesis and perhaps initially a different goal entirely. At any rate, Newton embarked on a thorough program of experimentation to figure out what the prism was doing to light. 

One can imagine him almost literally playing with prisms, screens, and lenses until he found a configuration that allowed him to formulate and investigate some definite hypotheses. (Newton once famously claimed that "I feign no hypotheses," but in truth one can hardly do science at all without them.) 

But only Newton saw what this implies: that refraction is then all there is to it

It's a common situation for experimental science: you might want to investigate a phenomenon but be unsure quite what the right questions are, let alone how to deploy your instruments and measuring devices to answer them. You need to develop a feeling for the system you're trying to study. 

Newton closed the "window-shuts" of his room, admitting a single narrow beam of sunlight through a hole, which passed into the prism. In the crucial experiment, Newton investigated the nature of the light after it exited the prism. If the light became colored because of some transformation produced by the prism, then a passage through a second prism might be expected to alter the light again. 

Newton used a board with a hole in it to screen off all the spectrum except for a single color — red, say — and then allowed that colored light to pass through the second prism. He found that this light emerged from the second prism refracted — bent at an angle — but otherwise unchanged. In other words, a prism seems only to bend (refract) light, leaving it otherwise unaltered. But it does so to different degrees (that is, at different angles) for different colors. 

This in itself was nothing new: the Anglo-Irish scientist Robert Boyle had said as much in his 1664 book "Experiments and Considerations Touching Colours," which Newton had read. But only Newton saw what this implies: that refraction is then all there is to it. 

The colors themselves are already in the white light, and all the prism does is to separate them out. As he put it, "Light consists of Rays differently refrangible" [meaning refractable]. The colors of the spectrum, then, "are not Qualifications [alterations] of Light … (as 'tis generally believed), but Original and connate properties." That was a bold interpretation: sunlight was not, so to speak, elemental, but compound. 

To test this idea, Newton used a lens to refocus a many-hued spectrum into a single, merged beam — which, he observed, was white. He also passed this reconstituted beam through another prism to reveal that it could again be split into a spectrum just as before. 

Newton explained how his observations could account for the rainbow, produced by the refraction and reflection of light through raindrops that act as tiny prisms. The colors of everyday objects, he added, arise because they reflect "one sort of light in greater plenty than another." 

— What is visible light?

— Are rainbows really arches?

— 20 inventions that changed the world

And the results explained the defects of lenses (Newton himself had become adept at making these by grinding glass), whereby refraction of different colors produces a defocusing effect called chromatic aberration. The Royal Society's secretary Henry Oldenburg told Newton that his report was met with "uncommon applause" when read at a gathering in February 1672. But not everyone appreciated it. 

After the paper was published in the society's Philosophical Transactions, its in-house curator of experiments, Robert Hooke , who considered himself an expert on optics, presented several criticisms (which we can now see were mistaken). Newton replied with lofty condescension, igniting a long-standing feud between the two men. 

One problem is that Newton's experiments, despite their apparent simplicity, are not easy to replicate: some, in England and abroad, tried and failed. But they have stood the test of time, a testament to the power of experiment to literally illuminate the unknown that, in the judgment of philosopher of science Robert Crease, gives Newton's so-called experimentum crucis "a kind of moral beauty."

Reprinted with permission from Beautiful Experiments: An Illustrated History of Experimental Science by Philip Ball, published by The University of Chicago Press. © 2023 by Quarto Publishing plc. All rights reserved.

Beautiful Experiments: An Illustrated History of Experimental Science - $25.82 on Amazon

Philip Ball's illustrated history of experimental science is a celebration of the ingenuity that scientists and natural philosophers have used throughout the ages to study — and to change — the world.

If you enjoyed this extract you can read another extract from the book: How 18th century scientists figured out fertilization

Philip Ball is a freelance writer and broadcaster, and was an editor at Nature for more than twenty years. He writes regularly in the scientific and popular media and has written many books on the interactions of the sciences, the arts, and wider culture, including "H2O: A Biography of Water "  and "The Music Instinct. "  His book "Critical Mass "  won the 2005 Aventis Prize for Science Books. Ball is also the 2022 recipient of the Royal Society’s Wilkins-Bernal-Medawar Medal for contributions to the history, philosophy, or social roles of science. He trained as a chemist at the University of Oxford and as a physicist at the University of Bristol, and he was an editor at  Nature  for more than twenty years. 

World's fastest microscope can see electrons moving

Heaviest antimatter particle ever discovered could hold secrets to our universe's origins

200 meteorites on Earth traced to 5 craters on Mars

Most Popular

• 2 Scientists collect high-resolution images of the North Star's surface for 1st time
• 3 Supercharged 'cocoon of energy' may power the brightest supernovas in the universe
• 4 AI and brain implant enables ALS patient to easily converse with family 'for 1st time in years'
• 5 Fallout from NASA's asteroid-smashing DART mission could hit Earth — potentially triggering 1st human-caused meteor shower

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 27 August 2024

Utilizing full-spectrum sunlight for ammonia decomposition to hydrogen over GaN nanowires-supported Ru nanoparticles on silicon

• Jinglin Li 1   na1 ,
• Bowen Sheng 2   na1 ,
• Yiqing Chen   ORCID: orcid.org/0000-0002-2686-5593 3   na1 ,
• Jiajia Yang 2 ,
• Ping Wang   ORCID: orcid.org/0000-0002-4716-5457 2 ,
• Yixin Li 1 ,
• Tianqi Yu 1 ,
• Liang Qiu 1 ,
• Ying Li 1 ,
• Jun Song   ORCID: orcid.org/0000-0003-3675-574X 3 ,
• Lei Zhu 1 ,
• Xinqiang Wang   ORCID: orcid.org/0000-0001-5514-8588 2 , 4 , 5 ,
• Zhen Huang 1 &
• Baowen Zhou   ORCID: orcid.org/0000-0003-2476-0322 1  

Nature Communications volume  15 , Article number:  7393 ( 2024 ) Cite this article

215 Accesses

Metrics details

• Photocatalysis

Photo-thermal-coupling ammonia decomposition presents a promising strategy for utilizing the full-spectrum to address the H 2 storage and transportation issues. Herein, we exhibit a photo-thermal-catalytic architecture by assembling gallium nitride nanowires-supported ruthenium nanoparticles on a silicon for extracting hydrogen from ammonia aqueous solution in a batch reactor with only sunlight input. The photoexcited charge carriers make a predomination contribution on H 2 activity with the assistance of the photothermal effect. Upon concentrated light illumination, the architecture significantly reduces the activation energy barrier from 1.08 to 0.22 eV. As a result, a high turnover number of 3,400,750 is reported during 400 h of continuous light illumination, and the H 2 activity per hour  is nearly 1000 times higher than that under the pure thermo-catalytic conditions. The reaction mechanism is extensively studied by coordinating experiments, spectroscopic characterizations, and density functional theory calculation. Outdoor tests validate the viability of such a multifunctional architecture for ammonia decomposition toward H 2 under natural sunlight.

Similar content being viewed by others

Greenhouse-inspired supra-photothermal CO 2 catalysis

Mechanistic analysis of multiple processes controlling solar-driven H 2 O 2 synthesis using engineered polymeric carbon nitride

Light-driven synthesis of C 2 H 6 from CO 2 and H 2 O on a bimetallic AuIr composite supported on InGaN nanowires

Introduction.

Ammonia decomposition (2NH 3  → N 2  + 3H 2 ) is promising for leveraging ammonia as a viable hydrogen carrier to effectively tackle the pressing challenges associated with hydrogen storage, transportation, and distribution because of its high hydrogen storage density (106 kg·m −3 ), ease of liquefaction (8–10 bars, 20 °C), and globally mature storage and transportation networks 1 , 2 , 3 , 4 . What is more, compared to other emerging liquid hydrogen carriers (e.g., CH 3 OH, HCOOH, and cyclohexane), the zero-carbon characteristic of ammonia decomposition delivers a perspective of constructing a carbon-neutral hydrogen system 2 , 3 . In general, thermo-catalysis is favorable for practically producing H 2 from ammonia because of its high productivity and reliability 5 . It however encounters extensive thermal input and harsh reaction conditions 6 . In contrast, photocatalysis offers a relatively green and eco-friendly method for on-site hydrogen generation from ammonia decomposition by utilizing solar energy as the driving force despite the limit of the intermittent nature of sunlight. Nevertheless, for pure photocatalysis, since a broad range of the solar spectrum such as infrared light can’t be absorbed to produce charge carriers because of their low energy, most of the solar energy is not effectively transformed into chemical energy 7 . Most recently, photo-thermal coupling has appeared as an innovative strategy for converting solar energy into chemical fuels by simultaneous utilization of charge carriers and heat 8 , 9 , 10 , 11 , 12 . In this case, ultraviolet photons with high energy enable the generation of charge carriers while visible- and infrared- light are highly favorable for heating the localized surface of the catalyst owing to their significant photo-thermal effect. Of note, the synergy of heat and charge carriers is highly promising for enabling a substantial reduction in the activation energy barrier of chemical process according to previous reports 8 , 13 . Such important discoveries shield light on breaking the bottleneck of sunlight-driven ammonia decomposition toward H 2 . The construction of a rational photo-thermal-coupled catalytic architecture is at the core yet still remains an extraordinary challenge.

Gallium nitride nanowires vertically aligned on silicon wafer (GaN NWs/Si) have emerged as a next-generation semiconductor platform for solar fuels generation from photocatalytic water splitting 14 , 15 , CO 2 reduction 16 , 17 , 18 , as well as methanol reforming 19 . It can be attributed to the following reasons: (i) At first, the optical properties of the GaN NWs/Si hybrid allow for a broad range absorption of the solar spectrum with alleviated photon scattering; (ii) Well-defined one-dimensional (1D) nanostructures facilitate the achievement of high localized surface temperature in a nano-confined environment under concentrated light illumination with shortened charge diffusion pathway, thus favoring surface redox reactions; (iii) The tunable surfaces (nitrogen- or metal-terminated) offer a flexible scaffold for manipulating the behavior of various chemical species; (iv) More importantly, earth-abundant silicon (Si), owing to the merits of highlight-absorption, chemical stability, thermal conductivity, has recently become a promising photo-thermal catalytic building block, especially if illuminated by concentrated light 20 . Together, the hybrid of GaN nanowire and silicon may be a suited candidate for assembling a rational photo-thermal architecture for sunlight-driven ammonia decomposition toward H 2 , especially when coupling with an appropriate co-catalyst.

Ruthenium (Ru) is an extensively studied catalyst for ammonia decomposition with high activity because of its suited binding with the intermediate species (neither too strongly nor too weakly) 21 , 22 , 23 . Hence, in this study, Ru nanoparticles (Ru NPs) were coupled with GaN NWs/Si to assemble a architecture for photo-thermal-coupling NH 3 decomposition toward H 2 . The synergy between charge carriers and photo-induced thermal energy of Ru NPs/GaN NWs/Si enabled the achievement of a light-induced substantial reduction in apparent activation energy ( E a ) for NH 3 decomposition, significantly decreasing from 1.08 eV to 0.22 eV. What is more, the temperature-dependent photoluminescence spectroscopy characterization showed that the recombination of charge carriers was also significantly lowered by the photo-thermal-coupled effect. As a result, a high hydrogen evolution rate of 3.98 mmol·cm −2 ·h −1 is attained under 5 W·cm −2 , which is nearly three orders of magnitude higher than that (0.004 mmol·cm −2 ·h −1 ) of the pure thermo-catalytic activity measured under the same temperature without light irradiation. Furthermore, because of the high efficiency of active sites and the unique surface properties, this architecture exhibits a high turnover number of > 3,400,750 mol H 2 per mole ruthenium over a long-term stability test of 400 h without measurable activity degradation. The operando spectroscopic characterizations and computational investigations show that Ru nanoparticles work in synergy with GaN to effectively stabilize the *NH 2 intermediate from NH 3 decomposition by photo-excited holes over the catalytic interface, thus switching the potential-determining step from *NH 2  + *H → *NH 2 to *NH + *H → *NH with a reduced Gibbs free energy. In situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and the local density of states (LDOS) analysis suggest that the photo-induced electron migrates from GaN to Ru for reducing the proton toward *H (H + + e − → *H), further facilitating H 2 generation. Outdoor tests using a low-cost resin lens validated the viability of such a multifunctional architecture for maximally utilizing natural solar energy to realize on-site H 2 generation from ammonia decomposition.

Assembly and characterization of Ru-decorated GaN NWs vertically aligned onto silicon

According to our previous work, 1D GaN NWs were controllably grown on a 4-inch silicon wafer by employing plasma-assisted molecule beam epitaxy (MBE) technology under N-rich conditions 24 , 25 . Ru NPs were subsequently immobilized onto GaN NWs/Si via a simple photo-deposition method (Supplementary Fig.  S1 and Experimental Section). As characterized by scanning electron microscope (SEM), the epitaxial GaN NWs decorated with Ru NPs were vertically aligned on the silicon wafer, featuring a length of about 950 nm with an averaged diameter of about 50 nm (Fig.  1A ). The well-defined 1D nanostructure renders GaN NWs with high surface area and short charge diffusion length, which is highly favorable for spatially decoupling photons absorption, charges separation, as well as surface chemical reactions. Compared to the pristine GaN NWs (Supplementary Fig.  S2 ), the overall morphology of nanowires is not obviously varied with the decoration of Ru NPs. The high-angle annular dark-field scanning transmission microscope (HAADF-STEM) image illustrates that the Ru NPs with the size of about 19 nm was randomly distributed on GaN NWs surface (Fig.  1B ). The lattice spacing of 0.26 nm is assigned to the (002) plane of GaN, in line with XRD patterns (Supplementary Fig.  S3 ), suggesting the c-axis growth direction of the nanowires 26 , 27 . The lattice spacing of 0.23 nm is attributed to the (100) plane of metallic Ru 28 . However, no typical peaks of Ru NPs were observed in XRD patterns, because of its low content (0.11 μmol·cm −2 ), as characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-OES). The energy dispersive X-ray spectroscopy (EDS) mapping further validated that Ru NPs were successfully assembled on the GaN NWs/Si platform (Fig.  1B ).

A 45°-tilted SEM image of Ru NPs-decorated GaN NWs/Si. HR: H 2 activity; TOF: turnover frequency; TON: turnover numbers. B HAADF-STEM and EDS mapping images of Ru NPs-decorated GaN NWs. High-resolution XPS spectra of ( C ) Ga 2 p , ( D ) N 1  s , ( E ) Ru 3 d . F Bader charge analysis between Ru and GaN. The yellow and cyan regions indicate the gain and loss of electronic charge respectively, with an isosurface of 0.008 e/Å 3 . Ga, blue; N, yellow; and Ru, salmon. Source data are provided as a Source Data file.

X-ray photoelectron spectroscopy (XPS) was carried out to investigate the chemical components of Ru NPs/GaN NWs/Si and the interaction between Ru NPs and GaN NWs (Supplementary Fig.  S4 ). The characteristic peaks of Ga 3 d and N 1  s are located at ~20 and ~397 eV, respectively (Figs.  1C, D ) 29 . The high-resolution X-ray photoelectron spectroscopy (HR-XPS) spectra of Ru 3 d in Fig.  1E confirmed the presence of metallic Ru species (281.3 eV). The peak located at 282.0 eV was assigned to the Ru-N bond. Further, the observable binding energy shifts of ~0.3 eV and ~0.1 eV in the HR-XPS spectra of Ga 2 p and N 1 s compared to that of pristine GaN are indicative of the electron redistribution between Ru NPs and GaN NWs. Bader charge analysis was conducted to confirm the above results. As shown in Fig.  1F , a discernible charge transfer is observed from Ru to GaN on the optimized geometry of Ru/GaN with a calculated value of 0.535e. As studied below, such an electronic interaction between Ru and GaN not only stabilizes the nanoparticles against agglomeration but also provides electronic transmission channels, thus catalytically facilitating the ammonia decomposition.

As one key component of the photo-thermal-coupling architecture, GaN can generate energetic carriers with sufficient redox potential for ammonia decomposition if excited by appropriate photons as characterized by photoluminescence (PL) spectroscopy (Fig.  2A ). The incorporation of Ru species can inhibit the recombination of photoinduced electron-hole pairs 30 . Time-resolution PL (TR-PL) spectroscopy further revealed that upon decoration with Ru species (Fig.  2B ), the average charge lifetime ( τ avr ) of GaN decreased from 2.02 ns to 1.81 ns, suggesting accelerated charge transfer 30 , 31 . The above results demonstrate that the decoration of Ru NPs onto GaN NWs is favorable for mediating the charge behavior to catalyze ammonia decomposition. The photo-thermal properties of the architectures were further studied using an infrared thermograph. As shown in Fig.  2C , the surface temperature of Ru NPs/GaN NWs/Si can reach 409.7 °C under 5 W·cm −2 , which is relatively higher than that of Ru NPs/Si (Supplementary Fig.  S5A ). Herein, GaN NWs contribute to the photothermal effect by alleviating the photon scattering due to the well-defined 1D nanostructure 32 , 33 . In contrast, when the Si substrate was replaced by sapphire (Supplementary Fig.  S5B ), the measured temperature dropped to 284.5 °C without varying any other conditions (Fig.  2C ). The results show that Si is indeed an ideal platform for assembling a photo-thermal architecture. The well-defined 1D nanostructure of GaN is beneficial to reducing the Rayleigh scattering, thus further increasing the surface temperature of the architecture without changing the illumination. Such a hierarchical architecture does not only provide energetic charge carriers but also enables high localized temperature. It thus holds a grand promise for photo-thermal-coupling ammonia decomposition toward H 2 , which will be elaborately studied next.

A PL spectroscopy of GaN NWs/Si decorated with/without Ru NPs recorded with pulse excitation of 80 MHz at a wavelength of 325 nm. B TRPL spectroscopy of GaN NWs decorated with/without Ru NPs by a time-correlated single photon counting technique. τ avr : average charge lifetime. C Infrared thermal images of Ru NPs/GaN NWs/Si, GaN NWs/Si, Ru NPs/Si, and Ru NPs/GaN TF/Sapphire surface under 5 W·cm −2 concentrated light illumination. Ru NPs loaded onto commercial GaN thin films on sapphire substrate is defined as Ru NPs/GaN TF/Sapphire. Source data are provided as a Source Data file.

Photo-thermal-coupling performance of ammonia decomposition toward H 2

The performance of Ru NPs/GaN NWs/Si for ammonia decomposition was tested in a sealed quartz chamber under atmospheric argon. A 300 W Xenon lamp equipped with a quartz lens was used as the light source. A commercial ammonia aqueous solution was used as the feedstock as water is a good medium for NH 3 storage and transportation under ambient conditions. Under concentrated light illumination, the aqueous ammonia solution was facilely evaporated due to the strong photo-thermal effect. The critical role of each component of the ternary Ru NPs/GaN NWs/Si architecture was first investigated (Fig.  3A ). In the absence of Ru species, the bare GaN NWs/Si platform is almost inactive for light-driven ammonia decomposition although charge carriers and photo-induced heat can be provided under concentrated light illumination at 5 W‧cm −2 (Fig.  3A ), suggesting that Ru species are essential for the reaction by serving as active sites. The hydrogen evolution rate was significantly enhanced by the immobilization of Ru NPs (Supplementary Figs.  S7 and S8 ). A maximum value of 1.77 mmol·cm −2 ·h −1 was achieved at a Ru loading of 0.11 μmol·cm −2 , corresponding to an optimal turnover frequency of 16091 h −1 , which is an intrinsic metric for evaluating the activity of the catalytic sites (Supplementary Figs.  S6 and S7 ). Herein, the average diameter of Ru NPs was measured to be ~19 nm (Supplementary Fig.  S8 ). A reduced H 2 activity of 0.98 mmol·cm −2 ·h −1 was observed when Ru loading increased up to 0.22 μmol·cm −2 (Supplementary Fig.  S6 ). It is primarily due to the undesired agglomeration of Ru NPs with an average diameter of > 86 nm (Supplementary Fig.  S8 ) 34 . Despite the high surface temperature arising from the significant photo-thermal effect of silicon, there is almost no hydrogen production over Ru/Si, suggesting the critical role of GaN NWs in offering energetic charge carriers (Supplementary Fig.  S9 ).

A H 2 evolution rate over Ru NPs/GaN NWs/Si, GaN NWs/Si, and Ru NPs/Si illuminated by a 300 W-xenon lamp under 5 W·cm −2 . B H 2 activity over Ru NPs/GaN NWs/Si under dark equipped with an external heating system and concentrated light-illuminating conditions without external heating. The architecture was maintained at the same temperature for better comparison of the performance between photo-thermal-coupling catalysis and pure thermocatalysis. C Arrhenius plots for H 2 evolution rate under dark and light conditions over Ru NPs/GaN NWs/Si. D H 2 evolution rate over Ru NPs/GaN NWs/Si under 5 W·cm −2 with/without cooling. E H 2 evolution rate over Ru NPs/GaN NWs/Si under light irradiation in different spectral ranges (full spectra, ultraviolet, visible, and infrared) with/without external heating source. The temperature of the external heating source is set to 280 °C. F Durability test over Ru NPs/GaN NWs under 4 W·cm −2 . Sample, ~0.5 cm 2 , ~0.36 mg·cm −2 ; atmospheric argon; 300 W Xenon lamp. Source data are provided as a Source Data file.

The light intensity-dependent H 2 activity was further measured to study the photo-thermal synergy. As illustrated in Fig.  3B , the H 2 evolution rate showed an increasing trend as the light intensity increased, and reached 3.98 mmol·cm −2 ·h −1 at 5 W·cm −2 with an appreciable turnover frequency (TOF) of 36,182 h −1 without any other energy inputs (Supplementary Fig.  S10 ). Such a great activity is nearly 1-2 orders of magnitude higher than state-of-the-art thermal or photocatalytic ammonia decomposition systems (Table  S1 ). To decouple the photo-excited carriers and photo-induced heat contribution, the catalytic properties of Ru NPs/GaN NWs/Si were both photo-catalytically and thermal-catalytically measured. First of all, light-induced heating was in operando recorded with an infrared thermograph as a function of light intensity (Supplementary Fig.  S11 ). The surface temperature of the as-designed architecture showed an increasing trend as the illumination intensity increased, varying from 274.1 °C at 3.0 W·cm −2 at up to 409.7 °C at 5.0 W·cm −2 . Shockingly, the photo-thermal-coupling activity is nearly 1000 times higher than that of pure thermo-catalysis under the same temperatures over the temperature range tested (Fig.  3B ). Herein, the photo-thermal-coupling activity was obtained by the only input of concentrated light while the thermo-catalysis was powered by external heating. Of note, as calculated by the Arrhenius equation, the apparent activation energy ( E a ) of NH 3 decomposition over Ru NPs/GaN NWs/Si is significantly reduced from 1.08 eV to 0.22 eV upon light illumination (Fig.  3C ). The above results suggested that the reaction proceeded via photocatalysis, which can be further promoted by the photoinduced thermal effect resulting from the concentrated visible- and infrared light. The influence of light wavelength on the reaction was also studied. As shown in Supplementary Fig.  S12 , under a measured reaction temperature of 270 °C set by external heating, the introduction of 275 nm under monochromatic light illumination of 29.8 mW·cm −2 in the system results in an enhanced H 2 evolution rate of 1.46 μmol·cm −2 ·h −1 with a high apparent quantum efficiency (AQE) of 1.19% over Ru NPs/GaN NWs/Si. It is much higher than that of the 535 nm under monochromatic light illumination of 285.1 mW·cm −2 . Therefore, it is reasonable to speculate that the high-energy photons of <365 nm that can produce energetic charge carriers are critical for superior activity. However, by employing an external cooling system to alleviate the photo-thermal effect of the reaction system (Fig.  S13 ), the measured catalytic activity sharply dropped from 3.98 to 0.06 mmol·cm −2 ·h −1 (Fig.  3D ). Thus, the photo-induced heat also plays an unignored role for promoting ammonia decomposition. Based on the results above, it is rationally hypothesized that for Ru NPs/GaN NWs/Si, upon concentrated sunlight illumination, high-energy ultraviolet is able to produce energetic charge carriers by exciting GaN NWs. Meanwhile, the remaining visible- and infrared light absorbed by the silicon substrate, accounting for a large proposition of the solar energy (~93%), contributed to heating the architecture and offered high-localized surface reaction temperature for ammonia decomposition. Charge carriers and heat work in synergy to promote the reaction by inducing a substantial reduction of activation barriers of ammonia decomposition and increasing the reaction temperature. Such a hypothesis was further validated by wavelength control experiments. The thermal contribution from various regions of the solar spectrum was first studied. As shown in Supplementary Fig.  S14 , the surface temperature of the architecture was measured by an infrared thermograph. It was found that the full-arc spectrum at 4 W·cm −2 can increase the architecture temperature up to 342.7 °C. By contrast, the surface temperature of the architecture dropped to 100.5 °C if an ultraviolet light filter was employed. Meanwhile, visible and infrared light can heat the architecture to 161.7 and 170.4 °C, respectively. In the absence of an external heat source, the hydrogen activity of Ru NPs/GaN NPs illuminated by ultraviolet light was only about 20% of the full spectrum (Fig.  3E ). The incorporation of the infrared and visible light did not show activity for ammonia decomposition toward H 2 . Notably, once an external heat source was applied for heating the reaction system (280 °C), the introduction of ultraviolet light can greatly improve the activity of H 2 up to 1.56 mmol·cm −2 ·h −1 , which is nearly 90% of the activity obtained under the full spectrum. These findings reveal the synergy between charge carriers induced by ultraviolet light and photo-induced heat as a result of visible light and infrared light played a vital role in the performance of Ru NPs/GaN NWs/Si.

As a key metric for practical application, the stability of the architecture was also examined (Fig.  3F ). A high turnover number (TON) of 3,400,075 moles of hydrogen per mole of Ru NPs was achieved after 400 h of light illumination. Of note, an H 2 :N 2 stoichiometric ratio of 3:1 was observed, suggesting the absence of the undesired side reaction. As characterized by XPS and TEM, there were no significant morphology and chemical component variations for this architecture after the stability test (Supplementary Fig.  S15 ). The aforementioned observations are indicative of the good stability.

Temperature-dependent photoluminescence (TD-PL) spectroscopy characterizations were conducted to study the photo-thermal effect on the reaction. It is observed that by increasing the measured temperature from 50 °C to 450 °C, the recombination of photoexcited e − /h + pairs was evidently inhibited (Fig.  4A ) 35 , 36 . Hence, the photo-thermal effect does not only promote the reaction by increasing the reaction temperature but also facilitates the separation of photoexcited e − /h + pairs, which is very beneficial for the reaction. Operando diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) was utilized to monitor the key intermediates of ammonia decomposition (Fig.  4B ). It is discovered that the peaks at around ~948 cm −1 and ~3255 cm −1 are assigned to the adsorbed *NH 3 species 1 , 37 , 38 . The peak intensity at around 1369 cm −1 arising from the *NH 2 intermediate increased with the irradiation time 39 , 40 , which is well matched with the EPR results (Supplementary Fig.  S16 ). It can be attributed to the continued deprotonation of *NH 3 toward *NH 2 by the photo-excited holes (NH 3 + h + → NH 2  + H + ), which had not yet reached steady-state condition even 25 min after since the start because of the saturation of ammonia in the cell. Of note, compared with pure thermal catalysis (Supplementary Fig.  S17 ), the accumulation rate of *NH 2 on the surface of the catalyst during the photo-thermal-coupling process is significantly faster (Supplementary Fig.  S18 ), further suggesting that the photo-thermal effect greatly promotes the activation and deprotonation of the reactant molecules. The above results demonstrate the viability of maximally utilizing solar energy to drive NH 3 decomposition toward H 2 by effectively utilizing photons at various regions (Fig.  4C ).

A TD-PL spectroscopy of Ru NPs/GaN NWs/Si. B Operando DRIFT spectra of ammonia decomposition over Ru NPs/GaN NWs/Si under light illumination of 4 W·cm −2 . C Schematic diagram of the synergy between charge carriers and photo-induced heat for promoting ammonia decomposition over Ru NPs/GaN NWs/Si. Source data are provided as a Source Data file.

Possible mechanism of ammonia decomposition

The electronic state of the catalytic interface can affect the reaction significantly. Thereby, the redistribution of photo-induced electrons at the interface between GaN and Ru was characterized by in situ irradiated XPS (ISI-XPS) (Fig.  5A ). It is clear that under light illumination, the binding energy of Ru 3 d illustrated a slightly negative shift. Conversely, a marked positive shift in the HR-XPS spectra of Ga 2 p and N 1 s was observed (Supplementary Fig.  S19 ). Herein, these observations validated that Ru NPs behave as effective electron sinks as reported 41 , 42 . The electron redistribution from GaN to Ru under light illumination is critical for superior activity 41 . NH 3 temperature-programmed desorption (NH 3 -TPD) characterizations were conducted to investigate the adsorption behavior of ammonia molecules. When GaN was decorated with Ru NPs, the desorption signal of NH 3 was evidently enhanced (Fig.  5B ). It is indicative that the incorporation of Ru species can promote the adsorption of NH 3 molecules onto the GaN NWs surface, thus favoring hydrogen evolution from ammonia decomposition. Operando DRIFT reveals the evolution track of ammonia at the molecular level (Fig.  4B and Supplementary Fig.  S20 ). Interestingly, the accumulation rate of *NH 2 intermediates on the pristine GaN is much lower than that of Ru NPs/GaN NWs/Si (Fig.  5C ), suggesting that the absence of Ru stabilizes the *NH 2 for further dehydrogenation, which will be discussed by DFT calculations next. Isotope experiments were conducted in NH 3 /D 2 O medium to elucidate the origin of hydrogen. It is found that H 2 almost originated from NH 3 (Supplementary Fig.  S21 ). Moreover, there was not an evident variation in reaction kinetics between NH 3 /H 2 O and NH 3 /D 2 O, which is indicative of no kinetic isotope effect (KIE) (Supplementary Fig.  S22 ). The ratio of H 2 and N 2 was detected online with the use of a reaction chamber linking the gas chromatography (GC) to prevent the interference of N 2 in the air. GC analysis of the product suggested a stoichiometric H 2 /N 2 ratio of 1/3 (Supplementary Fig.  S23 ), with no other byproducts aside from H 2 and N 2 . Based on the above results, it is reasonably speculated that water does not actively participate in the reaction; rather, it serves primarily as an ideal storage and transportation medium of NH 3 under ambient conditions, which is important for practical applications.

A ISI-XPS spectra of Ru 3 d with or without light illumination. B NH 3 -TPD spectra of bare GaN NWs and Ru NPs/GaN NWs. C Calculated slope change of the peak intensity of *NH 2 based on operando DRIFT spectra in Fig.  4B and Fig.  S20 . D LDOS for pristine GaN and Ru/GaN, respectively. The black dashed line indicates the position of the Fermi level. E The calculated free energy ∆G diagrams for NH 3 decomposition on GaN and Ru/GaN. The values in the figures indicate the energy difference for the potential-limiting step of the reaction. F Schematic diagram of ammonia decomposition process over the Ru/GaN interface. Source data are provided as a Source Data file.

DFT calculations were performed to gain insights into the reaction mechanism at the molecular level. Firstly, three optimal surface models of Ru (0001), GaN (10 \(\bar{1}\) 0), and Ru/GaN were constructed (Supplementary Fig.  S24 ). The electronic properties were analyzed by plotting the local density of states (LDOS) for GaN and Ru (Fig.  5D ). Pristine GaN with a large bandgap (3.4 eV) is generally not conducive to electron transfer in the reaction 43 . However, after decorating with Ru NPs, the metal states appeared near the Fermi level of GaN, enabling a high conductivity of this architecture. More importantly, the strong interaction between GaN and Ru arising from the electron redistribution formed a new state around the Fermi level for Ga and N atoms at the interface, thus facilitating the photoexcited electron transfer from GaN to Ru and its subsequent participation in the ammonia decomposition. This computational result was in well consistency with the ISI-XPS characterizations (Fig.  5A ). Furthermore, the ammonia decomposition pathway on the three surfaces was calculated and the results are shown in the Gibbs free energy diagram (Fig.  5E ). Upon the initial adsorption stage, the NH 3 molecule was strongly attached to the GaN surface, with the N atom binding to the Ga atom, and then a H atom was captured by the near N atom in GaN (Supplementary Fig.  S25 ). Of note, the NH 3 adsorption energy over the GaN is slightly reduced from −0.98 eV to −1.15 eV after the immobilization of Ru NPs (Supplementary Fig.  S26 and Table  S2 ), indicating an enhanced adsorption capacity of Ru/GaN for NH 3 molecule. It is well matched with the NH 3 -TPD measurements (Fig.  5B ). Following the step of *NH 3  → *NH 2 , *NH 2 intermediate was stabilized onto the catalytic interface for the subsequent decomposition process. Particularly, in the case of GaN, we observed that the potential-determining step (PDS) exhibited high endergonicity with a significant energy difference of 1.78 eV. In contrast, the presence of a Ru cluster on the GaN surface stabilized the *NH 2 intermediates and thus significantly reduced the barriers and shifted the PDS to the desorption of the second H atom, resulting in a smaller free energy change of only 0.58 eV (Fig.  5E and Supplementary Fig. S27 ). Based on the ISI-XPS and LDOS results (Fig.  5A and Fig.  5D ), the transfer of photoinduced electrons enables the electron-rich Ru sites to a lower ∆ G H value, which is a favor for the accumulation of *H for the final formation of H 2 (Fig.  5F ). What’s more, the adsorption energy of water molecule is much higher than that of NH 3 molecule over the Ru NPs-decorated GaN surface (Supplementary Figs.  S26 , S28 , and  S29 ), and significantly increase the energy barrier for H 2 O dissociation on both GaN and Ru/GaN surfaces compared to NH 3 decomposition (Supplementary Fig.  S30 ). Therefore, in this study, water primarily functions as a medium of ammonia rather than a hydrogen source, in line with the isotopic experimental results.

On-site hydrogen evolution under natural concentrated sunlight illumination

To assess the practical viability, the as-assembled architecture was tested under natural concentrated sunlight. The homemade experimental setup mainly consisted of a Fresnel lens, support frame, and quartz reaction chamber (Fig.  6A ). The natural sunlight was concentrated by a cheap and simple lens, which is beneficial for improving the performance and reducing the usage of the catalyst. As depicted in Fig.  6B and Supplementary Fig.  S31 , the H 2 evolution rate is directly related to the natural sunlight illumination conditions, which is varied from 0.07 mmol·cm −2 ·h −1 to 0.17 mmol·cm −2 ·h −1 , as a result of the varied light intensity. This observation suggests that the H 2 rate over the architecture is highly dependent on the light intensity. What’s more, the solar-to-hydrogen (STH) efficiency was also calculated, reaching an optimal value of 5% from 13:00 pm to 14:00 pm (Supplementary Fig.  S32 ). After 14 h of operation, San illustrious TON of 51,689 moles H 2 per moles Ru NPs was achieved under naturally concentrated sunlight conditions (Fig.  6C ). Such an outdoor test revealed the viability of utilizing natural sunlight for hydrogen production from ammonia. To step forward to practical application, as the priority, the fabrication cost of the architecture needs to be significantly reduced. Meanwhile, long-term stability is required for the architecture.

A Image of outdoor test setup equipped with Ru/GaN NWs/Si. B Activity and ( C ) TON of Ru NPs/GaN NWs for ammonia decomposition under concentrated natural sunlight without external heating, the inset in ( B ) is the digital picture of Ru NPs/GaN NWs/Si. Source data are provided as a Source Data file.

In summary, Ru NPs/GaN NWs/Si has demonstrated a virtual success in photo-thermal-coupling ammonia decomposition toward H 2 under concentrated sunlight illumination. The synergy of photo-excited charge carriers and photoinduced heat enabled a substantial reduction in the activation energy barrier for NH 3 decomposition. The architecture of Ru NPs/GaN NWs/Si showed a measurable H 2 rate of 3.98 mmol·cm −2 ·h −1 under 5 W·cm −2 by an increasing factor of nearly 1000 compared with pure thermocatalysis under the same tested temperature without light illumination. Meanwhile, the architecture exhibited a considerable TON of 3,400,750 mol H 2 per mol Ru without activity variation after 400 h of uninterrupted light illumination. Experimental, spectroscopic, and computational calculations disclosed the origin of the measurable performance of the architecture. Outdoor tests further confirmed the viability of this architecture for maximally utilizing the entire solar energy to produce hydrogen from ammonia.

MBE growth of GaN NWs/Si. MBE growth of GaN NWs/Si

GaN NWs were epitaxially grown on 4-inch silicon (111) wafer using a SVTA molecular beam epitaxy (MBE) system, equipped with a dual filament Knudsen cell for gallium source (Ga purity 99.99999%), a standard Knudsen cell for magnesium source (Mg purity 99.9999%), and a Veeco Unibulb radio frequency (RF) nitrogen plasma source (N 2 purity 99.9999%). The nitrogen plasma was operated with a constant N 2 gas flow of 1.0 sccm and RF power of 400 W, corresponding to a growth rate of 300 nm/h for GaN NWs. All GaN NWs were grown under N-rich growth conditions with a III/V ratio of 0.2. Before growth, the silicon wafer was firstly degassed in the growth chamber at 900 °C for 30 min. Then, 60 s surface nitridation was performed at 800 °C to form a few monolayers of Si x N y , which facilitates the nucleation of the following GaN base. Subsequently, unintentionally doped n-type GaN NWs were grown at 700 °C, followed by the growth of Mg-doped p-GaN NWs at 600 °C. During the growth of p-GaN NWs, Mg cell temperature was gradually varied from 230 °C to 270 °C, which is an efficient approach for controlling the diameter of GaN NWs. The resulting GaN NWs exhibit a p-n double-layer structure. The Mg element was successfully detected in the epitaxial GaN NWs by EDS mapping characterization (Supplementary Fig.  S33 ). The consumption of Ga, Mg, and N 2 is less than 200 mg, 0.6 mg, and 200 mL in each of these GaN nanowire samples growth.

Synthesis of Ru NPs/GaN NWs/Si

The deposition of Ru NPs was conducted in a sealed Pyrex chamber equipped with a quartz lid through a simple photo-deposition process. The GaN NWs supported by silicon wafer (~0.5 cm 2 ) was fixed at the bottom of the chamber, and then 50 mL methanol aqueous solution with a methanol/H 2 O (methanol, Shanghai Titan Technology Co., Ltd) volume ratio of 1/5, and a specified amount (5, 10, 20 μL…) of 0.2 M Ru precursor solution (RuCl 3 ·H 2 O, Shanghai Bide Pharmaceutical Technology Co., Ltd.) were added into the chamber. The chamber was subsequently evacuated and filled with argon to atmospheric pressure, followed by a full-arc 300 W Xe lamp irradiated for 30 min. At last, the sample was rinsed with distilled water and dried by compressed air. Notably, the amount of Ru was controlled by adjusting the content of Ru precursor solution (5, 10, 20 μL…), and the loading amount of Ru over GaN NWs/Si was precisely determined by ICP-OES, which is reported in Supplementary Fig.  S6 .

Characterization

X-ray diffraction (XRD) patterns were measured by a Bruker D8 Advance diffractometer (with Cu Kα, at 60 kV and 80 mA). Induced coupled plasma (ICP) characterization was measured to determine the loaded amount of Ru NPs by employing an AGILENT ICP-OES 730. X-ray photoelectron spectroscopy (XPS) was performed using ESCALAB 250xi non-monochromatic Al anodes, and the C 1 s peak at 284.8 eV was used as the internal standard for calibration. Scanning electron microscopy (SEM) images were captured with a Quattro ESEM (Thermo Fisher). PL and TR-PL spectroscopies were measured using an FLS980 (Edinburgh Instruments). TD-PL were measured using an FLS980 (Edinburgh Instruments) equipped with ADVANCED RESEARCH SYSTEMS (ARS) LT4 series standard continuous flow thermostats. Transmission electron microscopy (TEM) images were captured by employing a JEOL 2100 F microscope. HAADF-STEM images were obtained by a Thermo Fisher Scientific Talos F200X S/TEM with a Super-X EDS detector and operated at 200 kV. NH 3 -TPD characterization was conducted on an Autosorb-iQ-C chemisorption analyzer (Quantachrome, USA). Isotope characterizations were carried out using a TRACE 1310 gas chromatograph equipped with a 253Plus mass spectrometry module. In situ irradiated XPS was analyzed by ESCALAB 250xi non-monochromatic Al anodes using a 300 W Xe lamp as an irradiation source. In situ EPR measurement was conducted on a Bruker A300 (Germany) using 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap. DRIFT spectra were collected by using a Frontier FT-IR Spectrometer, PerkinElmer, equipped with an MCT detector and a 10-cm Demountable Gas Cell. In the process of the DRIFT characterization, Ru NPs/GaN NWs/Si were fixed in the Cell. The ammonia aqueous solution was injected into the Cell through a bubbling system. The background spectrum of the system was recorded when the reactant reached adsorption-desorption equilibrium on the catalyst surface. Of note, ammonia was in a saturated state in the cell at this time. The Cell was subsequently closed by cutting off the injection of the reactant. Then the photocatalyst surface was illuminated by a 300 W Xenon lamp with a light intensity of 5 W·cm −2 . The DRIFT data was recorded once every three minutes.

Performance evaluation

In the lab, hydrogen production from ammonia aqueous solution was evaluated in a 0.44 L homemade sealed quartz chamber. Prior to being placed at the bottom of the chamber, the photocatalyst (~0.5 cm −2 , ~0.36 mg cm −2 ) was thoroughly rinsed with distilled water and dried by compressed air. Subsequently, the chamber was evacuated and filled with atmospheric argon. 1 mL of ammonia aqueous solution (AR, 28%, Shanghai Titan Technology Co., Ltd.) was injected into the chamber. A 300 W Xe lamp equipped with a quartz lens was used as the light source and the illumination time was 30 min if not specifically noted. The surface temperature of the photocatalyst was recorded using infrared thermography (FOTRFIC 315, Shanghai Thermal Imaging Technology Co., Ltd.). The emissivity calibration procedure can be seen below: (i) A specific area of the catalysts was uniformly sprayed with acrylic resin. (ii) After waiting for 3 min, the catalyst was illuminated by a 300 W Xe lamp with a quartz lens. (iii) The emissivity of the infrared thermograph was set to 0.96, and the temperature of the coating position was recorded. (iv) An infrared thermograph was used to monitor the temperature of the uncoated position and adjust the emissivity ε until the recorded temperature was consistent with that of the coating position. The ε is, namely, the emissivity of the catalysts. The emissivity of all samples (Ru NPs/GaN NWs/Si, GaN NWs/Si, Ru NPs/Si, and Ru NPs/GaN TF/Sapphire) was roughly estimated to be around 0.8 according to the above procedure. For comparison, the thermo-catalytic experiments were carried out in an argon-filled tube furnace without light illumination. The wavelength-dependence experiments were measured using a 0.042 L stainless-steel cell equipped with a top sapphire window under different monochromatic light (275 nm and 535 nm) irradiation. During the reaction process, an external heating system was employed to maintain the stainless-steel cell at 270 °C monitored by a thermocouple. The light intensities of monochromatic light equipped with a quartz lens at wavelengths of 275 and 535 nm are 29.8 and 285.1 mW·cm −2 , respectively. For all measurements, the light irradiation area is determined as the area of the photocatalyst (0.42 cm 2 ). The reaction time of the monochromatic light was controlled at 3600 s. The outdoor test was performed by using a homemade setup (Fig.  6A ). The catalyst wafer was placed at the bottom of the chamber in a support frame. The Fresnel lens was used for concentrating sunlight. During the testing process, the Fresnel lens was adjusted to enable the catalyst wafer to obtain the maximum light intensity. Prior to the next cycle, the chamber was evacuated and filled with argon to exclude the generated hydrogen. The products were analyzed by employing a gas chromatograph (GC-9080, Sun) equipped with a thermal conductivity detector (TCD) for the quantitative detection of hydrogen and nitrogen components in samples. The H 2 evolution rate, TOF, and TON were calculated according to the following equations:

The optimal content of Ru over GaN NWs/Si was determined to be 0.11 μmol·cm −2 measured by ICP-OES.

The AQE ( φ ) was calculated by this equation:

where n is the number of involved electrons, the R is hydrogen evolution rate (Supplementary Fig.  S12 ), and I is the number of incident protons 8 , 44 . The light intensities ( P ) of monochromatic light equipped with a quartz lens at wavelengths of 275 and 535 nm are 29.8 and 285.1 mW·cm −2 , respectively. For all measurements, the light irradiation area ( S ) is determined as the area of the photocatalyst (0.42 cm −2 ). The reaction time ( T ) of the monochromatic light was controlled at 3600 s. The detailed calculation is shown below 8 , 44

Where E is the energy of photons , λ is the wavelength of using monochromatic light, h is the Plank constant, and c is the speed of light.

The kinetic isotope effects (KIE) were calculated by dividing the reaction rates of H 2 production from NH 3 /H 2 O by the reaction rates of H 2 production from NH 3 /D 2 O.

The solar energy conversion efficiency was calculated by the following equation:

Where the ΔH 0 (94.6 kJ·mol −1 ) is the standard reaction enthalpy changes of ammonia decomposition. The area of catalyst ( S ) is about 30.8 cm −2 . Considering the fluctuation of natural light, the light intensity is averaged within one hour, for example, the average light intensity from 13:00 to 14:00 was determined to be 7.97 W·cm −2 .

Computational methods. We constructed 4 × 4 Ru (0001) surface with 4 atomic layers and 4 × 2 GaN (10 \(\bar{1}\) 0) surface with six atomic layers to represent the pure Ru and GaN systems, respectively. Additionally, Ru/GaN was created by depositing a small cluster of 6 Ru atoms on GaN (10 \(\bar{1}\) 0). Various Ru/GaN configurations were examined, and we identified the most stable configuration, as illustrated in Supplementary Fig.  S24 , for subsequent calculations. During the structural relaxation process, the bottom two layers of Ru (0001) and the bottom three layers of GaN slabs were kept fixed in their bulk positions. To minimize image interactions, a vacuum spacing of at least 12 Å was added along the normal direction of the surface in all slab models. The reaction intermediate for NH 3 decomposition and H 2 O dissociation on those models are shown in Supplementary Figs.  S25 , S27 – S29 .

Spin-polarized density functional theory (DFT) calculations were performed using the Vienna Ab Initio Simulation Package (VASP) 45 , 46 . The projector-augmented wave (PAW) method was adopted to describe the interaction between valence electrons and ions 47 . Perdew-Burke-Ernzerhof (PBE) functional was employed to present the exchange-correlation in the Kohn-Sham equation 48 , 49 . Van der Waals (vdW) interactions were included using Grimme’s DFT-D3 method 50 , 51 . A plane-wave basic set with a kinetic energy cutoff of 500 eV was used. For all slabs, a 2 × 2 × 1 Mokhorst-Pack k-point grid was implemented to sample the Brillouin zone 52 . All structures converged until the atomic forces and the total energies reached 0.02 eV/Å and 10 −5  eV, respectively.

In this study, the free energies were computed using the computational hydrogen electrode (CHE) model 53 . The Gibbs free energy of adsorption ∆G was calculated by:

where E ad is the adsorption energy defined by:

ΔZPE and ΔS represent the changes in zero-point energy and entropy, respectively. The temperature, denoted as T , was set to the room temperature.

Data availability

All data generated in this study are provided in the Supplementary Information/Source Data file.  Source data are provided in this paper.

Fang, H. et al. Dispersed surface Ru ensembles on MgO(111) for catalytic ammonia decomposition. Nat. Commun. 14 , 647 (2023).

Article   ADS   CAS   PubMed   PubMed Central   Google Scholar  

Li, Y. et al. Low temperature thermal and solar heating carbon‐free hydrogen production from ammonia using nickel single atom catalysts. Adv. Energy Mater. 12 , 2202459 (2022).

Article   CAS   Google Scholar  

Kocer, T., Oztuna, F. E. S., Kurtoğlu, S. F., Unal, U. & Uzun, A. Graphene aerogel-supported ruthenium nanoparticles for CO x -free hydrogen production from ammonia. Appl. Catal. A-Gen. 610 , 117969 (2021).

Lucentini, I., Garcia, X., Vendrell, X. & Llorca, J. Review of the decomposition of ammonia to generate hydrogen. Ind. Eng. Chem. Res. 60 , 18560–18611 (2021).

Kanaan, R., Affonso Nóbrega, P. H., Achard, P. & Beauger, C. Economical assessment comparison for hydrogen reconversion from ammonia using thermal decomposition and electrolysis. Renew. Sust. Energ. Rev. 188 , 113784 (2023).

Sun, S. et al. Ammonia as hydrogen carrier: advances in ammonia decomposition catalysts for promising hydrogen production. Renew. Sust. Energ. Rev. 169 , 112918 (2022).

Iwase, A., Ii, K. & Kudo, A. Decomposition of an aqueous ammonia solution as a photon energy conversion reaction using a Ru-loaded ZnS photocatalyst. Chem. Commun. (Camb.) 54 , 6117–6119 (2018).

Article   CAS   PubMed   Google Scholar  

Luo, S. et al. Triggering water and methanol activation for solar-driven H 2 production: interplay of dual active sites over plasmonic ZnCu alloy. J. Am. Chem. Soc. 143 , 12145–12153 (2021).

Christopher, P., Xin, H., Marimuthu, A. & Linic, S. Singular characteristics and unique chemical bond activation mechanisms of photocatalytic reactions on plasmonic nanostructures. Nat. Mater. 11 , 1044–1050 (2012).

Article   ADS   CAS   PubMed   Google Scholar  

Ding, X., Liu, W., Zhao, J., Wang, L. & Zou, Z. Photothermal CO 2 catalysis toward the synthesis of solar fuel: from material and reactor engineering to techno-economic analysis. Adv. Mater. n/a , 2312093 (2024).

Article   Google Scholar  

Liu, S. et al. Efficient thermal management with selective metamaterial absorber for boosting photothermal CO 2 hydrogenation under sunlight. Adv. Mater. 36 , 2311957 (2024).

Xiong, H. et al. Highly efficient and selective light-driven dry reforming of methane by a carbon exchange mechanism. J. Am. Chem. Soc. 146 , 9465–9475 (2024).

Li, Y. et al. Rh/InGaN 1-x O x nanoarchitecture for light-driven methane reforming with carbon dioxide toward syngas. Sci. Bull. 69 , 1400–1409 (2024).

Zhou, B. & Sun, S. Approaching the commercial threshold of solar water splitting toward hydrogen by III-nitrides nanowires. Front. Energy 18 , 122–124 (2024).

Li, Y., Sadaf, S. M., Zhou, B. & Ga X)N/Si nanoarchitecture: an emerging semiconductor platform for sunlight-powered water splitting toward hydrogen. Front. Energy 18 , 56–79 (2023).

Rashid, R. T. et al. Tunable green syngas generation from CO 2 and H 2 O with sunlight as the only energy input. Proc. Natl Acad. Sci. USA   119 , e2121174119 (2022).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Zhou, B. et al. Highly efficient binary copper−iron catalyst for photoelectrochemical carbon dioxide reduction toward methane. Proc. Natl. Acad. Sci. USA   117 , 1330–1338 (2020).

Li, J. & Zhou, B. Aulr@InGaN nanohybrid for artificial photosynthesis of C 2+ fuel and H 2 O 2 . Chin. Sci. Bull. 69 , 3–6 (2024).

Li, J. et al. Nickel-iron bimetal as a cost-effective cocatalyst for light-driven hydrogen release from methanol and water. ACS Catal. 13 , 10153–10160 (2023).

Zhang, C. et al. Silicon nanostructure arrays: an emerging platform for photothermal CO 2 catalysis. Acta Phys. -Chim. Sin. 40 , 2304004 (2024).

Google Scholar  

Le, T. A., Do, Q. C., Kim, Y., Kim, T.-W. & Chae, H.-J. A review on the recent developments of ruthenium and nickel catalysts for CO x -free H 2 generation by ammonia decomposition. Korean J. Chem. Eng. 38 , 1087–1103 (2021).

Chen, C. et al. Ru-based catalysts for ammonia decomposition: a mini-review. Energy Fuels 35 , 11693–11706 (2021).

Bradford, M. C., Fanning, P. E. & Vannice, M. A. Kinetics of NH 3 decomposition over well dispersed Ru. J. Catal. 172 , 479–484 (1997).

Li, J. et al. Oxynitride-surface engineering of rhodium-decorated gallium nitride for efficient thermocatalytic hydrogenation of carbon dioxide to carbon monoxide. Commun. Chem. 5 , 107 (2022).

Wang, Z. et al. Photocatalytic syngas production from bio-derived glycerol and water on AuIn-decorated GaN nanowires supported by Si wafer. Green Chem. 25 , 288–295 (2023).

Chu, S. et al. Photoelectrochemical CO 2 reduction into syngas with the metal/oxide interface. J. Am. Chem. Soc. 140 , 7869–7877 (2018).

Chu, S. et al. Tunable syngas production from CO 2 and H 2 O in an aqueous photoelectrochemical cell. Angew. Chem. Int. Ed. 55 , 14262–14266 (2016).

Li, C. et al. Photohole-oxidation-assisted anchoring of ultra-small Ru clusters onto TiO 2 with excellent catalytic activity and stability. J. Mater. Chem. A 1 , 2461 (2013).

Dong, W. J. et al. CuS-decorated gan nanowires on silicon photocathodes for converting CO 2 mixture gas to HCOOH. J. Am. Chem. Soc. 143 , 10099–10107 (2021).

Zhang, Z. et al. Stable and highly efficient photocatalysis with lead-free double-perovskite of Cs 2 AgBiBr 6 . Angew. Chem. Int. Ed. 58 , 7263–7267 (2019).

Shen, Q. Y. et al. Spatially separated photoinduced charge carriers for the enhanced photocatalysis over the one-dimensional yolk-shell In 2 Se 3 @N-C nanoreactor. ACS Catal. 11 , 12931–12939 (2021).

Dong, W. J. et al. Silver halide catalysts on GaN nanowires/Si heterojunction photocathodes for CO 2 reduction to syngas at high current density. ACS Catal. 12 , 2671–2680 (2022).

Zhou, B. et al. Gallium nitride nanowire as a linker of molybdenum sulfides and silicon for photoelectrocatalytic water splitting. Nat. Commun. 9 , 3856 (2018).

Article   ADS   PubMed   PubMed Central   Google Scholar  

Low, J., Yu, J., Jaroniec, M., Wageh, S. & Al-Ghamdi, A. A. Heterojunction photocatalysts. Adv. Mater . 29 , 1601694 (2017).

Zhou, B. et al. Light-driven synthesis of C 2 H 6 from CO 2 and H 2 O on a bimetallic AuIr composite supported on InGaN nanowires. Nat. Catal. 6 , 987–995 (2023).

Wang, Y. et al. Deep ultraviolet light source from ultrathin GaN/AlN MQW structures with output power over 2 watt. Adv. Opt. Mater. 7 , 1801763 (2019).

Chen, W., Qu, Z., Huang, W., Hu, X. & Yan, N. Novel effect of SO 2 on selective catalytic oxidation of slip ammonia from coal-fired flue gas over IrO 2 modified Ce–Zr solid solution and the mechanism investigation. Fuel 166 , 179–187 (2016).

Wang, Y. et al. Single–atom Ir 1 supported on rutile TiO 2 for excellent selective catalytic oxidation of ammonia. J. Hazard. Mater. 432 , 128670 (2022).

Ali, S. et al. Synergistic effect between copper and cerium on the performance of Cu x -Ce 0.5- x -Zr 0.5 ( x = 0.1–0.5) oxides catalysts for selective catalytic reduction of NO with ammonia. Appl. Catal. B 210 , 223–234 (2017).

Sun, H., Wang, H. & Qu, Z. Construction of CuO/CeO 2 catalysts via the ceria shape effect for selective catalytic oxidation of ammonia. ACS Catal. 13 , 1077–1088 (2023).

Yang, Y. et al. Light-induced redox looping of a rhodium/Ce x WO 3 photocatalyst for highly active and robust dry reforming of methane. Angew. Chem. Int. Ed. 61 , e202200567 (2022).

He, C. et al. Constructing matched active sites for robust photocatalytic dry reforming of methane. Chem 9 , 3224–3244 (2023).

Kibria, M. G. & Mi, Z. Artificial photosynthesis using metal/nonmetal-nitride semiconductors: current status, prospects, and challenges. J. Mater. Chem. A 4 , 2801–2820 (2016).

Wang, H. et al. High quantum efficiency of hydrogen production from methanol aqueous solution with PtCu-TiO 2 photocatalysts. Nat. Mater. 22 , 619–626 (2023).

Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59 , 1758–1775 (1999).

Article   ADS   CAS   Google Scholar  

Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54 , 11169–11186 (1996).

Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50 , 17953–17979 (1994).

Article   ADS   Google Scholar  

Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77 , 3865–3868 (1996).

Perdew, J. P. et al. Atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46 , 6671–6687 (1992).

Grimme, S., Antony, J., Ehrlich, S. & Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 132 , 154104 (2010).

Article   ADS   PubMed   Google Scholar  

Grimme, S., Ehrlich, S. & Goerigk, L. Effect of the damping function in dispersion corrected density functional theory. J. Comput. Chem. 32 , 1456–1465 (2011).

Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 13 , 5188 (1976).

Article   ADS   MathSciNet   Google Scholar  

Nørskov, J. K. et al. Origin of the overpotential for oxygen reduction at a fuel-cell cathode. J. Phys. Chem. B 108 , 17886–17892 (2004).

Download references

Acknowledgements

The authors are thankful for the financial support by National Key Research and Development Program of China (2023YFB4004900), Shanghai Pilot Program for Basic Research–Shanghai Jiao Tong University (No.21TQ1400211), Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (No. SL2022MS007), National Natural Science Foundation of China (No.22109095), and Shanghai Municipal Major Research Program. B. S., P. W., and X. W. are thankful for the financial support from Beijing Outstanding Young Scientist Program (No.BJJWZYJH0120191000103), Beijing Natural Science Foundation (No.Z200004), and Nation Natural Science Foundation of China (No.6230031805). Y. C. and J. S. acknowledge the financial support by Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant (RGPIN-2017-05187) Computing resource by Compute Canada.

Author information

These authors contributed equally: Jinglin Li, Bowen Sheng, Yiqing Chen.

Authors and Affiliations

Key Laboratory for Power Machinery and Engineering of Ministry of Education, Research Center for Renewable Synthetic Fuel, School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China

Jinglin Li, Yixin Li, Tianqi Yu, Hu Pan, Liang Qiu, Ying Li, Lei Zhu, Zhen Huang & Baowen Zhou

State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Nano-Optoelectronics Frontier Center of Ministry of Education (NFC-MOE), Peking University, Beijing, China

Bowen Sheng, Jiajia Yang, Ping Wang & Xinqiang Wang

Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, QC, Canada

Yiqing Chen & Jun Song

Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu, China

Xinqiang Wang

Collaborative Innovation Center of Quantum Matter, School of Physics, Peking University, Beijing, China

You can also search for this author in PubMed   Google Scholar

Contributions

Conceptualization: J.L. and B.Z. Methodology: J.L., B.S., Y.C., P.W., L.Z., J.S., X.W., H.P., and B.Z. Investigation: J.L., Y.C., B.S., J.Y., Y.X.L., T.Y., L.Q., Y.L., H.P., and B.Z. Visualization: J.L. Funding acquisition: J.S., X.W., and B.Z. Project administration: Z.H. and B.Z. Supervision: B.Z. Writing–original draft: J.L., Y.C., and B.Z. Writing–review & editing: J.L. and B.Z.

Corresponding authors

Correspondence to Ping Wang , Jun Song , Xinqiang Wang or Baowen Zhou .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Peer review

Peer review information.

Nature Communications thanks Eun Duck Park and the other, anonymous, reviewers for their contribution to the peer review of this work. A peer review file is available.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary information, peer review file, source data, source data, rights and permissions.

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/ .

Reprints and permissions

About this article

Cite this article.

Li, J., Sheng, B., Chen, Y. et al. Utilizing full-spectrum sunlight for ammonia decomposition to hydrogen over GaN nanowires-supported Ru nanoparticles on silicon. Nat Commun 15 , 7393 (2024). https://doi.org/10.1038/s41467-024-51810-y

Download citation

Received : 26 January 2024

Accepted : 16 August 2024

Published : 27 August 2024

DOI : https://doi.org/10.1038/s41467-024-51810-y

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

• Search Menu
• Sign in through your institution
• Volume 533, Issue 3, September 2024 (In Progress)
• Volume 533, Issue 2, September 2024
• Advance Access
• MNRAS Letters homepage
• MillenniumTNG Project Special Issue
• NAM Plenary Speakers Virtual Issue
• MNRAS Student Awards
• Advanced Articles
• Why Publish
• Author Guidelines
• Submission Site
• Read & Publish
• Developing Countries Initiative
• Author Resources
• Self-Archiving policy
• About Monthly Notices of the Royal Astronomical Society
• Editorial Board
• About the Royal Astronomical Society
• Journals on Oxford Academic
• Books on Oxford Academic

Article Contents

1 introduction, 2 modelling the arc spectrum, 3 implementation, 4 precision of the calibration, 5 conclusions.

• < Previous

Wavelength calibration of arc spectra using intensity modelling

• Article contents
• Figures & tables
• Supplementary Data

L. A. Balona, Wavelength calibration of arc spectra using intensity modelling, Monthly Notices of the Royal Astronomical Society , Volume 409, Issue 4, December 2010, Pages 1601–1605, https://doi.org/10.1111/j.1365-2966.2010.17403.x

• Permissions Icon Permissions

Wavelength calibration for astronomical spectra usually involves the use of different arc lamps for different resolving powers to reduce the problem of line blending. We present a technique which eliminates the necessity of different lamps. A lamp producing a very rich spectrum, normally used only at high resolving powers, can be used at the lowest resolving power as well. This is accomplished by modelling the observed arc spectrum and solving for the wavelength calibration as part of the modelling procedure. Line blending is automatically incorporated as part of the model. The method has been implemented and successfully tested on spectra taken with the Robert Stobie spectrograph of the Southern African Large Telescope.

Wavelength calibration of astronomical spectra in the visible is usually performed using hollow cathode arc lamp spectra. The thorium lamp is most often used at high resolving power due to its numerous spectral features over the whole visible and near-infrared domains. Thorium is dominated by a single isotope and has no hyperfine structure, which leads to narrow, highly symmetric line profiles. For these reasons, ThNe and ThAr hollow cathode lamps have become the standard for wavelength calibration of astronomical spectrographs at high resolving powers. For moderate and low resolving powers, however, severe line blending occurs and lamps producing less rich spectra, such a CuAr, need to be used. The problem of line blending is solved by using a line list which is as free from blending as possible ( Lovis & Pepe 2007 ; Murphy et al. 2007 ).

The standard procedure in calibrating the wavelength scale of a spectrum is to identify the arc lines (usually by eye), measure their pixel positions and plot the laboratory wavelengths as a function of pixel positions. The method is the same as that used many decades ago for photographic spectra. The pixel location is determined by fitting the arc line with some suitable function such as a Gaussian. Problems arise when the line is blended. The definitions of ‘position’ and ‘wavelength’ then become problematical because the arc line is no longer symmetrical and the wavelength at peak intensity is not the same as given in a table of laboratory wavelengths. The inclusion of blended lines whose position is assumed to coincide with the laboratory wavelength of the principal component results in a calibration precision significantly worse than the intrinsic random noise limit ( de Cuyper & Hensberge 1998 ).

The usual way of correcting for line blending is to identify unblended lines and use them to calculate an effective wavelength for the blended lines. This is only possible if there are a sufficient number of unblended lines close to the blended line. The effective wavelength calculated in this way depends on the resolving power and separate wavelength tables are required for different resolving powers.

At sufficiently low resolving powers, the number of unblended lines is greatly reduced and one is forced to use an arc which produces fewer lines in the required spectral region. The type of arc which fulfils these conditions is severely limited and often there are stretches of the spectrum where the calibration is very poor or non-existent. The number of useful arc lines can be increased by using two different arc lamps simultaneously, but one usually finds that even this solution is not entirely satisfactory. These difficulties are well known, but no attempt has been made to resolve these problems.

It occurred to us that the blending problem might be solved by incorporating line blending in a synthetic model of the arc spectrum. Given the instrumental line profile, the line wavelengths and the approximate linewidth, one can use non-linear optimization to best match the synthetic spectrum to the observed spectrum. This can only be done if we know the wavelength calibration. However, if we begin with an approximate calibration, we can use non-linear optimization to derive the wavelength corrections as well. This method makes full use of the available data and, besides resolving the blending problem, should also result in a more precise calibration than the traditional method. However, the main advantage would be that one could use the rich thorium spectrum at all resolving powers, which would also largely eliminate poorly covered wavelength regions.

The method just described has never been attempted. The difficulty lies in how to incorporate the wavelength calibration in the non-linear optimization technique. We solved this problem by dividing the spectrum into a number of segments and assuming that within each segment the wavelength correction is a constant. Another problem is that it is not possible to solve for the optimal parameters for many dozens, perhaps hundreds of individual arc lines as this leads to numerical difficulties. Our solution to this problem is to measure beforehand, with the highest resolving power, the relative peak intensities of the arc lines. Given this information, the number of free parameters is reduced enormously and the only unknown is the intensity scalefactor.

In this paper we describe how this new wavelength calibration technique has been implemented on the Robert Stobie spectrograph (RSS) of the Southern Africa Large Telescope (SALT). We first of all describe in Section 2 the mathematical model that we use to describe the observed arc spectrum, given the relative peak intensities of the arc lines. In Section 3 we discuss how the relative intensities can be measured. In Section 4 we discuss the precision of the wavelength calibration thus derived. Finally, in Section 5 we present a step-by-step description of how we have implemented the new method.

To use the new method one needs to create an approximate model of the arc spectrum and use non-linear optimization to solve for the free parameters required to match the observed spectrum. We initially thought to use a wavelength-calibrated observed arc spectrum for this purpose. However, it is likely that the instrumental linewidth in such a template spectrum will not match the observed spectrum. Moreover, the linewidth in the template and the observed spectrum are likely to vary differently with wavelength. The most serious difficulty is, however, that we could not find a suitable mathematical representation of the problem which would allow a solution of the wavelength calibration using an observed arc as the template spectrum.

The problem can be resolved by using a synthetic arc spectrum as a template. In order to construct a synthetic arc spectrum, it is necessary to have good laboratory wavelengths, a matching instrumental line profile and good relative peak intensities. In this section we will describe the mathematical model assuming that such a template is available. We will discuss how the template can be created in the next section.

We can construct an effective pixel number for each segment using, for example, the centroid of the segment. Using this number, we can calculate an effective wavelength from the nominal polynomial. We call this the nominal wavelength of the segment. Given the values of a 2 for each segment, we can then find a better approximation to λ i and, if necessary, repeat the procedure using the corrected wavelengths instead of the nominal polynomial. In practice, we found that such an iteration is not necessary.

For the method to be implemented, a synthetic template of the arc spectrum needs to be created. To do this, we need to know h 0, j , the relative arc intensities. Unfortunately, this is not as easy to determine as it might appear because the sensitivity of the spectrograph varies across the spectrum. In other words, the relative intensities of a pair of widely separated arc lines depend on their pixel positions. However we are solving for a very limited wavelength region, all we need to ensure is that the relative intensities are accurate over reasonably small wavelength regions. In this section we describe how the relative intensities can be obtained. We also describe how one can obtain a first approximation to the nominal polynomial by using the grating angle. This, in turn, allows for reliable and fully automated arc line identification.

The relative intensities of arc lines can be obtained by measuring peak intensities from an arc spectrum taken at high resolving power. The procedure need only be done once and can be largely automated using suitable code. To correct for the effect described in the previous paragraph, we need spectra with considerable wavelength overlap. The code should only measure relative intensities in, say, the middle part of the spectrum. The wavelength overlap should be sufficient so that at least one arc line in common can be used to continue the solution. The aim is to produce a table giving the laboratory wavelength, λ 0, j , and the relative peak intensity, h 0, j , for each arc line. Though the procedure need only be done once, it should perhaps be repeated from year to year to take into account possible intensity variations caused by aging of the lamp. We implemented this procedure for the CuAr and ThAr lamps.

Generally speaking, for a given grating, the wavelength of the central pixel on the detector is a function of the grating angle, θ. If some time is invested in calibrating the central wavelength as a function of θ, this information is already of great use even for manual identification purposes. However, in our technique automated line identification is, in any case, a vital component because we need to know the coefficients of the nominal polynomial, λ i ,P . For this purpose, just knowing the approximate central wavelength is not sufficient. We need to be able to obtain the approximate coefficients of the nominal polynomial (in our case a quadratic) from θ.

The above relationships are not yet sufficiently accurate for our purposes because the grating angle θ is generally not well measured and changes in temperature and flexure limit the accuracy of the derived values of b 0 , b 1 and b 2 . The main effect is that the central wavelength, represented by b 0 , may be offset by 1 or 2 Å. To correct for this effect, we construct a synthetic spectrum using b 0 , b 1 and b 2 determined from equation (5) and cross-correlate it with the observed spectrum to obtain the correct value for b 0 . Once b 0 is obtained with sufficient accuracy, arc identification, at least for the highest peaks, is relatively simple. We use these identifications to further refine b 0 , b 1 and b 2 .

Having obtained a reasonably accurate nominal polynomial, we now have to decide on how many segments are required to cover the wavelength range of interest. In conventional calibrations, 20–80 data points are typically used. Since we need to define the wavelength correction curve as accurately as possible, the larger the number of segments the better. Against this, we need to ensure that there are sufficient pixels in each segment so that a solution is possible. Some segments may not include arc lines; these are ignored. Furthermore, only pixels which are known to contain an arc line in the line list are used (we used the NOAO iraf line list). In this way we avoid fitting to arc lines that have no wavelengths. Since the saturation intensity is known, we also avoid pixels which are saturated.

In the RSS the CCD mosaic has 6144 unbinned columns, excluding gaps between the CCDs. (However, observations are nearly always obtained with a binning factor of 2 for the columns). Since a minimum of about 200 pixels per segment are required for a good solution, the number of segments should not exceed 30. In our implementation we use a total of 48 segments, but there is an overlap with half of the previous and half of the next segment. Thus there are only 24 independent segments. These numbers can be changed quite easily, but we found them to be suitable in our case.

In the RSS, the useful spectrum covers the entire width of the CCD, but at the lowest resolving power (grating PG0300, resolving power ≈400), the spectrum occupies only half the width of the CCD. It is important to sample the useful range with at least 20 segments, so in this case the number of pixels per segment was reduced. One has to tailor the number of segments and the number of pixels per segment to suit the particular case.

We are now ready to solve for a 0 , a 1 and a 2 in equation (3) for each segment. As a first approximation we use a nominal (constant) value for the linewidth parameter, a 1 , which is the typical linewidth parameter for the given resolving power and set a 2 to zero. We then use χ 2 non-linear optimization to minimize the error term in equation (3) and obtain the best estimates for a 0 , and corrections for a 1 and a 2 for each segment. We use the Levenberg–Marquard algorithm as implemented in the GNU Scientific Library (GSL), but other methods can be used. A successful solution from one segment provides starting values for the neighbouring segment. Generally speaking there is normally no problem with convergence except perhaps for segments at extreme ends or when the lines are very weak. We begin the solution at the centre of the spectrum and work towards both ends.

With values of a 2 obtained for each segment, we can plot a graph of a 2 as a function of the nominal wavelength, λ, for that segment. Note that a 2 is the difference between the true wavelength and the wavelength given by the nominal polynomial. An example of a calibration curve for the PG3000 grating (resolving power ≈4200) is shown in Fig. 1 together with a smooth curve through the points. In Fig. 2 we show examples of the observed and fitted arc spectrum for the highest and lowest resolving powers available on the RSS.

Wavelength correction, δλ (or a 2 ), as a function of nominal wavelength, λ, for the CuAr arc and the PG3000 grating. The wavelengths are in Ångstroms.

Portions of observed (circles) and fitted (curve) CuAr arc spectra for PG3000 (top) and PG0300 (bottom).

Our implementation is fully automated and is available at the telescope. The fits file contains all the necessary information. The software extracts the arc, uses the grating angle to obtain a first approximation of the nominal polynomial, identifies the arc lines, corrects the coefficients and applies the above algorithm to obtain a 0 , a 1 and a 2 for each segment. The wavelength calibration curve ( a 2 as a function of nominal wavelength) is displayed, as well as the intensity fit to the arc. The wavelength at the central column is shown as a function of time to alert the observer to flexure of the spectrograph. Also shown is the line broadening as a function of wavelength so that the observer is aware of possible focus changes across the spectrum. All this is done only a second or two after the observation. The software can also be used off-line, in which case it simply reads a list of fits files, identifies them as arc or target spectra, extracts the spectra and produces fully calibrated target spectra with no user intervention at all. A full night's work can be processed in little more than 10 min. The user has full access to a variety of graphic tools which can be used to verify the results.

We noticed using the new method that the calibration curve is consistently reproduced in detail in spectra taken with the same settings at widely different times. Fine features which occur in a few regions of the spectrum and which were originally thought to be due to noise are repeated from frame to frame. An example is the bump seen at λ≈ 4100 Å in Fig. 1 . These features are clearly real, in the sense that they are repeatable. We have not studied them, but believe they could be due to incorrect wavelengths. To enable a better representation, we used a Hermite interpolation polynomial which has been smoothed, as shown in Fig. 1 . An ordinary polynomial, which does not fit the fine features, can also be used. This increases the standard deviation of the residuals by about 20–30 per cent relative to the use of a Hermite polynomial. In this section we describe how we have measured the precision of the calibration and how it compares with calibrations obtained using the conventional method.

It is difficult to determine the precision of the wavelength calibration. The GSL implementation of the Levenberg–Marquard algorithm returns the standard deviations of a 0 , a 1 and a 2 (or more correctly, the standard deviations of the corrections to these coefficients). The error of a 2 is less than 0.01 Å in the example of Fig. 1 (the typical value is only 0.002 Å). Even for the lowest resolving power (PG0300) the standard error of a 2 is typically only 0.02 Å. However, these errors are unrealistic because the analysis assumes that there are no errors in any other parameter.

For a realistic error estimate one obtains three successive arc exposures and uses the first and last exposures to calibrate the central exposure. The idea is to interpolate the solutions of the two outer exposures in order to correct for possible instrumental drift. We know what the wavelengths of the arc lines should be, and can therefore calculate the error in the calibration. It would be incorrect to judge the precision of the calibration if it incorporates instrumental drift. However, instrumental drift can be completely eliminated by simply using the same arc spectrum for all three exposures. Using this thought experiment, it is easy to see that the calibration error, free of instrumental drift, is simply the difference between the measured wavelength and the wavelength obtained from the fitted curve. This, in fact, is the method that is always used in the literature to estimate the uncertainty in the wavelength calibration.

It is certainly easy to do calculate the uncertainty in this way, but it clearly depends on how the calibration is modelled. A polynomial of higher degree will generally produce a smaller uncertainty. Somehow, the order of the polynomial that is used has to be justified. In our case we can justify the Hermite polynomial fit because we clearly see the same fine detail from spectrum to spectrum. If we believe that the fine detail is due to some problem, we should instead use a simple polynomial fit. The typical standard deviation of the residuals from the smoothed Hermite curve for the CuAr arc is shown in Table 1 . Also shown are minimum and maximum standard deviations. These numbers should be increased by about 25 per cent for a polynomial fit.

The first three columns give the grating name, the resolving power R and the dispersion (in Å per unbinned pixel). The number of frames, N , used to calculated the calibration error is given as well as σ, the average residual standard deviation (in Å) for the CuAr spectrum. The last two columns give the minimum and maximum standard deviations (in Å).

From the table, we see that the typical standard deviation per calibration point runs from about 0.006 to 0.035 Å for PG3000 (0.007 to 0.044 Å for a polynomial fit). For a resolving power R ≈ 4100, the same as PG3000, a standard deviation of 0.02–0.07 Å seems to be the typical value when the traditional procedure is used ( Bochanski et al. 2009 ). The method described here therefore leads to an increased precision of about a factor of 2.

An increase in precision is to be expected because the new method makes use of all available information, not just the information contained in the vicinity of the arc peaks. Nevertheless, we do not regard this as the main motivation for the method. The main reason for using the method is to overcome the blending problem and to use a spectrum such as ThAr for all resolving powers, providing good coverage at all wavelengths.

We can summarize the wavelength calibration technique described in this paper as follows.

(i) Measure the relative intensities of the arc lines at the highest available resolving power. These intensities need not be consistent over a wide wavelength range, but just over the range of a segment. Construct a list of wavelengths and relative intensities.

(ii) From information provided in the fits header, which includes the grating name and the grating angle, calculate the approximate coefficients of the nominal, polynomial ( equation 5 ).

(iii) Using this equation and a table of laboratory wavelengths and relative intensities, construct a template spectrum for the full observed wavelength range using a typical linewidth.

(iv) Cross-correlate the template spectrum with the observed spectrum to obtain a better estimate of b 0 , the constant term in the nominal polynomial. Use the improved polynomial to locate arc lines, which in turn leads to improved values of the nominal polynomial coefficients.

(v) Divide the spectrum into a number of segments and determine the wavelength correction, a 2 , for each segment by solving equation (3) using non-linear χ 2 optimization.

(vi) Fit a smooth curve to a 2 as a function of effective wavelength of the segment. Together with the improved nominal polynomial, this defines the wavelength calibration.

The method outlined here has been implemented in the SALT software and is completely automated. We make sure that all necessary information, such as the grating name and angle, are in the fits headers. The spectrum is automatically located and extracted optimally. The software runs at the telescope to produce fully calibrated spectra not only of the arc lines, but also of subsequent target spectra. It is also a valuable tool for correcting the focus and controlling the quality of spectra taken at the telescope.

The method leads to improved precision of the wavelength calibration. However, the most important advantage is that it is no longer necessary to use a variety of arc lamps to obtain sufficiently unblended arc lines over a limited wavelength range. In fact, the ThAr lamp, which is normally used only at high resolving power because of the richness of its spectrum, offers the best precision for all gratings and is perfectly usable even at the lowest resolving power. This is not possible in the traditional method.

There are, of course, difficulties with the method which also apply to conventional methods. For example, there may be saturated arc lines and it is important that the software deals with this correctly. It is easy enough to identify problematical regions of the spectrum and simply flag these to ensure that they have no effect on the solution. It is important that only pixels within a certain range of the tabulated arc wavelengths are used to avoid fitting unknown lines or other features. Very weak lines also pose problems and may give rise to spurious results if not carefully treated.

The method requires the use of uncorrected wavelengths and it is possible that slight bumps in the calibration curve might be due to the use of wavelengths corrected for blending. This slight problem, which only occurs in very few wavelength regions, requires further attention.

Email alerts

Astrophysics data system, citing articles via.

• Recommend to your Library
• Advertising and Corporate Services
• Journals Career Network

Affiliations

• Online ISSN 1365-2966
• Print ISSN 0035-8711
• Copyright © 2024 The Royal Astronomical Society
• About Oxford Academic
• Publish journals with us
• University press partners
• What we publish
• New features  
• Open access
• Institutional account management
• Rights and permissions
• Get help with access
• Accessibility
• Advertising
• Media enquiries
• Oxford University Press
• Oxford Languages
• University of Oxford

Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide

• Copyright © 2024 Oxford University Press
• Cookie settings
• Cookie policy
• Privacy policy
• Legal notice

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

• Previous Article
• Next Article

Quantum Defect and Fine Structure in the Arc Spectrum of Rubidium—An Experiment

• Article contents
• Figures & tables
• Supplementary Data
• Peer Review
• Reprints and Permissions
• Cite Icon Cite
• Search Site

K. L. Luke , S. George , A. W. Tucker; Quantum Defect and Fine Structure in the Arc Spectrum of Rubidium—An Experiment. Am. J. Phys. 1 May 1974; 42 (5): 400–407. https://doi.org/10.1119/1.1987709

Download citation file:

• Ris (Zotero)
• Reference Manager

Using a relatively inexpensive, commercially available rubidium lamp, we obtained the first 11, 7 and 19 lines of the sharp, principal, and diffuse series respectively from the arc spectrum of rubidium. It is shown that the following three student exercises can be performed by using the data obtained: (a) identification of the sharp, principal, and diffuse series of rubidium; (b) verification of Rydberg's formula for rubidium, in so doing determine the quantum defect and series limit for the sharp, principal and diffuse series, respectively; and (c) verification of the dependence of the splitting due to spin-orbit interaction of the levels on   n *   as given by the Landé formula. From the results, this experiment is recommended for an advanced optics and spectroscopy or quantum physics laboratory .

Citing articles via

Submit your article.

Sign up for alerts

• Online ISSN 1943-2909
• Print ISSN 0002-9505
• For Researchers
• For Librarians
• For Advertisers
• Our Publishing Partners  
• Physics Today
• Conference Proceedings
• Special Topics

pubs.aip.org

• Privacy Policy
• Terms of Use

Connect with AIP Publishing

This feature is available to subscribers only.

Sign In or Create an Account

Stack Exchange Network

Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

What is an "arc" spectrum ?

I sometimes hear about astronomers using an arc spectrum to calibrate observations. For example a "He-Ar arc spectrum". What is an "arc" in this context? I assume it's nothing got to do with angles (arcmin, arcsec, etc.).

• observational-astronomy
• amateur-observing
• spectroscopy

• $\begingroup$ @ConradTurner, you could add some more details and make an answer out of your comment ! $\endgroup$ –  Py-ser Commented Dec 1, 2015 at 14:53
• $\begingroup$ @LocalFluff See Conrad's answer. The arc refers to a discharge lamp. $\endgroup$ –  ProfRob Commented Dec 2, 2015 at 8:24

An arc spectrum is one produced by a discharge lamp where the discharge is through ionised gas, in the case of He-Ar a mixture of Helium and Argon, which produces a predictable line emission spectrum.

They are often used to provide a calibration spectrum for spectrometers .

• $\begingroup$ An electric arc, in air, between two iron electrodes, is also used as a source of reference emission lines... $\endgroup$ –  DJohnM Commented Dec 5, 2015 at 5:56

You must log in to answer this question.

Not the answer you're looking for browse other questions tagged observational-astronomy amateur-observing spectroscopy spectra ..

• Featured on Meta
• We've made changes to our Terms of Service & Privacy Policy - July 2024
• Bringing clarity to status tag usage on meta sites
• Do we really want a [debunk] tag?

Hot Network Questions

• Dress code for examiner in UK PhD viva
• How can judicial independence be jeopardised by politicians' criticism?
• Has the US said why electing judges is bad in Mexico but good in the US?
• Why does a halfing's racial trait lucky specify you must use the next roll?
• AM-GM inequality (but equality cannot be attained)
• no match for 'operator==' in GCC 12
• Using \tl_put_right with grouping from latex3 explsyntax
• Weird SMS. Help!
• Ring Buffer Implementation in C++
• How long does it take to achieve buoyancy in a body of water?
• Stuck on Sokoban
• How to logging Preferences library
• How can moral disagreements be resolved when the conflicting parties are guided by fundamentally different value systems?
• Which version of Netscape is this, on which OS?
• Do the amplitude and frequency of gravitational waves emitted by binary stars change as the stars get closer together?
• Reference request: acceleration/curvature of curve in metric space
• Parody of Fables About Authenticity
• Image Intelligence concerning alien structures on the moon
• Are there any polls on the opinion about Hamas in the broader Arab or Muslim world?
• Could someone tell me what this part of an A320 is called in English?
• Why does flow separation cause an increase in pressure drag?
• Does Vexing Bauble counter taxed 0 mana spells?
• Maximizing the common value of both sides of an equation
• "TSA regulations state that travellers are allowed one personal item and one carry on"?

• Skip to primary navigation
• Skip to main content
• Skip to primary sidebar

• FREE Experiments
• Kitchen Science
• Climate Change
• Egg Experiments
• Fairy Tale Science
• Edible Science
• Human Health
• Inspirational Women
• Forces and Motion
• Science Fair Projects
• STEM Challenges
• Science Sparks Books
• Contact Science Sparks
• Science Resources for Home and School

How to Make a Rainbow with a Prism

June 21, 2019 By Emma Vanstone Leave a Comment

Visible or white light is made up of a range of colours each with a different wavelength . One way to see the different colours is to use a prism to split the light. When white light enters the prism it slows down and changes direction. The amount the light changes depends on the wavelength. Red light changes direction the least and violet the most.

Visible light is the part of the electromagnetic spectrum we can see. Each colour has a range of wavelengths. Red has a long wavelength and low frequency and violet has a short wavelength and high frequency.

What is a prism?

A prism is a triangular block of glass or perspex which splits light into its constituent colours.

When light enters a prism it is refracted. Each colour of the spectrum is refracted by a different amount and the colours are dispersed ( spread out ) allowing you to see them.

A prism is a great way to demonstrate visually that white light is actually made up of 7 different colours.

How to split white light with a prism

What you need to split light

Triangular prism

White cardboard

Large sheet of white paper

Dark coloured cardboard

Tape or glue

Large tray or sheet of thick card

How to use a prism

If it’s not a sunny day, you can use a torch.

Use the dark card to create a slit over a sheet of white card. Place the card so sunlight shines through giving a thin beam of light.

Place the prism over the light and rotate it until you can see the light split into the spectrum of colours.

Why does a prism split light?

White light, which enters the prism, is a mixture of different wavelengths, which get bent ( refracted ) by different amounts though the prism, allowing them to be seen separately.

Facts about light waves

Light travels in straight lines.

It takes 8 minutes and 20 seconds for light to reach Earth from the Sun.

Light waves can travel through a vacuum.

Visible light is a form of electromagnetic radiation.

Light waves are much faster than sound waves.

Wavelengths of the visible spectrum of light range from 400nm ( violet end ) to 700nm (red end ).

More learning activities about light

Find out how to make a rainbow using a hosepipe !

Reverse the direction of arrows with this easy light refraction experiment .

Learn about how light travels in straight lines by making a light maze .

Last Updated on May 7, 2022 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

Leave a reply cancel reply.

Your email address will not be published. Required fields are marked *

Basic Characteristics of Arc Spectrum in P-GTAW Process

• First Online: 01 May 2019

Cite this chapter

• Yiming Huang 3 &
• Shanben Chen 4  

302 Accesses

Spectral analysis can realize the simultaneous detection of various elements with the advantages of fast response speed and low detection limit. Therefore, it has been widely used in metallurgy, geology, materials and medicine and other industries. With the development of electronic technology and computer technology, emission spectrum analysis technology has been developed rapidly. The characteristics of the arc welding process can be diagnosed by means of emission spectroscopy. Based on analyzing the characteristics of spectral lines of each element, this chapter proposes to extract spectral lines accurately and scientifically based on clustering algorithm, so as to avoid the interference of external factors such as zero drift and insufficient resolution of instruments. In order to obtain the optimal results, the k-medoids clustering method is improved to realize automatic acquisition of number of distinct categories and intelligent selection of initial points. In addition, the spectral distance suitable for spectral data was proposed as the measurement function. The centers obtained by clustering, namely the atomic and ion spectral lines of each element, are preliminarily studied. Furthermore, the influence of welding process parameters on the spectral lines is explored.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Subscribe and save.

• Get 10 units per month
• Download Article/Chapter or eBook
• 1 Unit = 1 Article or 1 Chapter
• Cancel anytime
• Available as PDF
• Read on any device
• Instant download
• Own it forever
• Available as EPUB and PDF
• Durable hardcover edition
• Dispatched in 3 to 5 business days
• Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Yu H, Chen H, Xu Y et al (2013) Spectroscopic diagnostics of pulsed gas tungsten arc welding plasma and its effect on weld formation of aluminum-magnesium alloy. Spectrosc Lett 46(5):350–363

Article   MathSciNet   Google Scholar  

Yu H, Chen S (2011) A study of arc length in pulsed GTAW of aluminum alloy by means of arc plasma spectrum analysis. In: Robotic welding, intelligence and automation. Springer, Berlin, Heidelberg, pp 219–227

Google Scholar  

Yu H, Song J, Zhang G et al (2014) The effects of arc length on welding arc characteristics in al–mg alloy pulsed gas tungsten arc welding. In: International conference on robotic welding, intelligence and automation. Springer, Cham, pp 321–335

Yu H, Ye Z, Zhang Z et al (2013) Arc spectral characteristics extraction method in pulsed gas tungsten arc welding for Al-Mg alloy. J Shanghai Jiaotong Univ 11:1

Yu H, Xu Y, Lv N, Chen H, Chen S (2013) Arc spectral processing technique with its application to wire feed monitoring in Al–Mg alloy pulsed gas tungsten arc welding. J Mater Process Technol 213:707–716

Article   Google Scholar  

Yu H, Xu Y, Song J, Pu J, Zhao X, Yao G (2015) On-line monitor of hydrogen porosity based on arc spectral information in Al–Mg alloy pulsed gas tungsten arc welding. Opt Laser Technol 70:30–38

Yu H, Ye Z, Chen S (2013) Application of arc plasma spectral information in the monitor of Al–Mg alloy pulsed GTAW penetration status based on fuzzy logic system. Int J Adv Manuf Technol 68:2713–2727

Huang Y, Wu D, He Y, Lv N, Chen S (2016) The selection of arc spectral line of interest based on improved K-medoids algorithm. In: IEEE workshop on advanced robotics and its social impacts (ARSO) IEEE, pp 106–109

Chang CI (2000) An information-theoretic approach to spectral variability, similarity, and discrimination for hyperspectral image analysis. IEEE Trans Inf Theory 46(5):1927–1932

Download references

Author information

Authors and affiliations.

School of Materials Science and Engineering, Tianjin University, Tianjin, China

Yiming Huang

Shanghai Jiao Tong University, Shanghai, China

Shanben Chen

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Yiming Huang .

Rights and permissions

Reprints and permissions

Copyright information

© 2020 Springer Nature Singapore Pte Ltd.

About this chapter

Huang, Y., Chen, S. (2020). Basic Characteristics of Arc Spectrum in P-GTAW Process. In: Key Technologies of Intelligentized Welding Manufacturing. Springer, Singapore. https://doi.org/10.1007/978-981-13-7549-1_3

Download citation

DOI : https://doi.org/10.1007/978-981-13-7549-1_3

Published : 01 May 2019

Publisher Name : Springer, Singapore

Print ISBN : 978-981-13-7548-4

Online ISBN : 978-981-13-7549-1

eBook Packages : Intelligent Technologies and Robotics Intelligent Technologies and Robotics (R0)

Share this chapter

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Publish with us

Policies and ethics

• Find a journal
• Track your research

Chemical Science

Visible light photoflow synthesis of a cu( ii ) single-chain polymer nanoparticle catalyst †.

* Corresponding authors

a Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstraße 15, 76131 Karlsruhe, Germany E-mail: [email protected]

b School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, 4000 Brisbane, QLD, Australia E-mail: [email protected] , [email protected]

c Centre for Materials Science, Queensland University of Technology (QUT), 2 George Street, 4000 Brisbane, QLD, Australia

d Centre for Advanced Imaging, The University of Queensland (UQ), Building 57 Research Road, 4072 Brisbane, QLD, Australia

e Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany E-mail: [email protected]

We herein pioneer the visible light ( λ max = 410 nm) mediated flow synthesis of catalytically active single-chain nanoparticles (SCNPs). Our design approach is based on a copolymer of poly(ethylene glycol) methyl ether methacrylate and a photocleavable 2-((((2-nitrobenzyl)oxy)carbonyl)amino)ethyl methacrylate monomer which can liberate amine groups upon visible light irradiation, allowing for single-chain collapse via the complexation of Cu( II ) ions. We initially demonstrate the successful applicability of our design approach for the batch photochemical synthesis of Cu( II ) SCNPs and transfer the concept to photoflow conditions, enabling, for the first time, the continuous production of functional SCNPs. Critically, we explore their ability to function as a photocatalyst for the cleavage of carbon–carbon single and double bonds on the examples of xanthene-9-carboxylic acid and oleic acid, demonstrating the advantageous effect SCNPs can provide over analogous small molecule catalysts.

Supplementary files

• Supplementary information PDF (11428K)
• Crystal structure data CIF (175K)

Article information

Download Citation

Permissions.

Visible light photoflow synthesis of a Cu( II ) single-chain polymer nanoparticle catalyst

S. Gillhuber, J. O. Holloway, K. Mundsinger, J. A. Kammerer, J. R. Harmer, H. Frisch, C. Barner-Kowollik and P. W. Roesky, Chem. Sci. , 2024, Advance Article , DOI: 10.1039/D4SC03079F

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence . You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content .

Social activity

Search articles by author.

This article has not yet been cited.

Advertisements

LZ experiment sets new record in search for elusive dark matter

Dr Theresa Fruth, from the School of Physics, prepares to descend a mile underground at the LZ experiment facility in South Dakota, USA.

Figuring out the nature of dark matter, the invisible substance that makes up most of the mass in our universe, is one of the greatest unsolved puzzles in modern physics. New results from the world’s most sensitive dark matter detector, LUX-ZEPLIN (LZ), have narrowed down possibilities for one of the leading dark matter candidates: weakly interacting massive particles, or WIMPs.

LZ, led by the United States Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), hunts for dark matter from a cavern nearly one mile underground at the Sanford Underground Research Facility in South Dakota. The experiment’s new results have set further limits on what WIMPs could be.

Dr Theresa Fruth from the School of Physics at the University of Sydney was instrumental in commissioning the LZ detector in South Dakota and is an active participant in the hunt for dark matter at the LZ experiment. She has worked on the project for nine years, including during her time at the University of Oxford and University College London.

“This detector is the best asset we have anywhere in the world in our hunt for WIMP dark matter over coming years. This result shows how sensitive the detector is and how useful it will be in helping us to solve this most intriguing of scientific puzzles,” she said.

LZ’s central detector in a surface lab clean room before delivery underground. Photo: Matthew Kapust/Sanford Underground Research Facility

Dark matter, so named because it does not emit, reflect, or absorb light, is estimated to make up 85 percent of the mass in the universe but has never been directly detected, though it has left its fingerprints on multiple astronomical observations.

Dr Fruth said: “We wouldn’t exist without this mysterious yet fundamental piece of the universe; dark matter’s mass contributes to the gravitational attraction that helps galaxies form.”

In the new result, the team found no evidence of WIMPs above 9 giga-electronvolts/c2 (GeV/c2), which is 1.6 x 10-26 kilograms, about ten times the mass of a proton.

“While finding ‘nothing’ doesn’t sound like much of a result, this is hugely important in narrowing down where we could find direct evidence of dark matter,” Dr Fruth said.

“Will dark matter fit snugly into the Standard Model of particle physics, or will its discovery need us to rewrite our theoretical models? We simply don’t know yet.”

The important new data has been presented today at physics conferences in Chicago, USA, and São Paulo, Brazil. A paper will be prepared for peer-review in coming weeks.

“If you think of the search for dark matter like looking for buried treasure, we’ve dug almost five times deeper than anyone else has in the past,” said Professor Scott Kravitz, LZ’s deputy physics coordinator and a professor at the University of Texas at Austin. “That’s something you don’t do with a million shovels, you do it by inventing a new tool.”

Researchers sit between two outer layers of LZ during construction. Photo: Matthew Kapust/Sanford Underground Research Facility

Professor Chamkaur Ghag, LZ spokesperson and professor University College London said: “These are new world-leading constraints by a sizable margin on dark matter and WIMPs. We know we have the sensitivity and tools to see whether they’re there as we search lower energies and accrue the bulk of this experiment’s lifetime.”

The experiment’s sensitivity to faint interactions helps researchers reject potential WIMP dark matter models that don’t fit the data, leaving fewer places for WIMPs to hide.

This result is also the first time that LZ has applied “salting”– a technique that adds fake WIMP signals during data collection. By camouflaging the real data until “unsalting” at the very end, researchers can avoid unconscious bias and keep from overly interpreting or changing their analysis.

“We’re pushing the boundary into a regime where people have not looked for dark matter before,” said Scott Haselschwardt, the LZ physics coordinator and a recent Chamberlain Fellow at Berkeley Lab who is now an assistant professor at the University of Michigan. “There’s a human tendency to want to see patterns in data, so it’s really important when you enter this new regime that no bias wanders in. If you make a discovery, you want to get it right.”

LZ uses 10 tonnes of liquid xenon at 175 Kelvin (minus 98.15 degrees) to provide a dense, transparent material for dark matter particles to potentially bump into. The hope is for a WIMP to knock into a xenon nucleus, causing it to move, much like a hit from a cue ball in a game of pool. By collecting the light emitted during such interactions by the detector’s 494 light sensors, LZ could capture WIMP signals with other rare events.

LZ is a collaboration of about 250 scientists from 38 institutions in the United States, United Kingdom, Portugal, Switzerland, South Korea, and Australia.

Dr Fruth leads the only Australian-based research group working on LZ. She is also a collaborator at the  Australian dark matter detector  (SABRE South) being built in an active gold mine in Stawell, Victoria.

LZ Completes TPC Assembly from Sanford Lab on Vimeo .

Declaration

LZ is supported by the US Department of Energy, Office of Science, Office of High Energy Physics and the National Energy Research Scientific Computing Center, a DOE Office of Science user facility. LZ is also supported by the Science & Technology Facilities Council of the United Kingdom; the Portuguese Foundation for Science and Technology; the Swiss National Science Foundation, and the Institute for Basic Science, Korea. More than 38 institutions of higher education and advanced research provided support to LZ. The LZ collaboration acknowledges the assistance of the Sanford Underground Research Facility.

Media contact

• +61 474 269 459
• [email protected]

Related articles

Downloading nasa's dark matter data from above the clouds, the hunt for dark matter: sydney joins arc centre of excellence, student astronomer finds galactic missing matter.

• Study Abroad Get upto 50% discount on Visa Fees
• Top Universities & Colleges
• Abroad Exams
• Top Courses
• Read College Reviews
• Admission Alerts 2024
• Education Loan
• Institute (Counselling, Coaching and More)
• Ask a Question
• College Predictor
• Test Series
• Practice Questions
• Course Finder
• Scholarship
• All Courses
• B.Sc (Nursing)

Rainbow: Spectrum of Light, Formation and Experiments

Jasmine Grover

Senior Content Specialist

Rainbow is a kind of spectacular optical effect that results in one of the amazing shows of light on Earth. It refers to an arc of multiple colors or a spectrum of light that is formed in the sky as a result of reflection, refraction, and the dispersion phenomenon of light in the water droplets. We can observe rainbows in the sky after rainfall when the sunlight strikes a raindrop. We can also see rainbows around sea spray, fog, or even waterfalls. It does not exist in a particular spot in the sky and therefore it is an optical illusion. The view of the rainbow depends on various factors such as the angle of sunlight and the place you are standing at. In this article, we will have a look at the formation of the rainbow and an experiment pertaining to the formation of a rainbow.

Read More: Applications of Thermodynamics

Read More: Wave Power

What is a rainbow?

Rainbow is a well-known optical phenomenon that leads to the formation of a glorious sight of a multicolor arc in the sky. This spectrum is formed due to the process of refraction of sunlight from a droplet of rain. It is a great demonstration of the fact that light has a spectrum of wavelengths, which is each associated with a different color. Rainbow can be observed not only on rainy days but on sunny days too when one is near a fountain or a waterfall. 

A rainbow's radius can be determined by the refractive index of the water droplet through which the sunlight passes. Here, the refractive index can be understood as the measure of the bending of a ray of light which is also referred to as refraction as it passes from one medium to another for instance from air to water. A droplet having a higher refractive index will produce a rainbow with a small radius. Rainbows that are formed from sea spray are smaller than the ones formed by rain droplets. This is because salt water has a higher refractive index than freshwater. 

Also Read:  

Colors of Rainbow

Rainbows are formed as a result of the dispersion of white light which splits into seven colors after passing through a raindrop. The seven primary colors of the rainbow are arranged in a band one above the other in a horizontal manner. The seven colors are:

• The acronym used to remember the order of the colors of the rainbow is VIBGYOR.

However, many a time "indigo" color is too similar to blue to be truly distinguished. When all the colors of the rainbow mix together, it appears to us as white light. For instance, sunlight appears white to us. When sunlight hits a droplet of water, some part of the light is reflected. Light with different wavelengths comes together to comprise the electromagnetic spectrum. All the colors are reflected at varying angles. Therefore, a spectrum is dispersed in order to produce a rainbow. 

• The red color has the longest wavelengths of all the colors, i.e. approximately 650 nanometres. It is on the outer side of the rainbow.
• Violet color has the shortest wavelength which is about 650 nanometers and therefore it usually appears in the inner arch of the rainbow.

Formation of a Rainbow

Rainbows are formed when sunlight, a white light, gets scattered by a droplet of water such as fog or raindrop by a process known as refraction. When the light from the sun changes its direction as it passes from a denser medium (denser than air) like a raindrop. The refracted light then enters the raindrop and is reflected from the back of its surface and again undergoes refraction as it leaves the drop to reach our eyes.

Our sunlight is formed of light of various wavelengths and colors which travel at varying speeds when they pass through a medium. Hence, the white light splits into different colors. The colors with longer wavelengths are towards the red end of the spectrum while the shorter wavelengths have a blue or violet hue. When the sunlight passes through the raindrop at angles that are approximately equal to two degrees, the color gets split from red to violet. The colors do seem to mix and merge and therefore might appear as a blur. Each rainbow is unique in its aspect as each angle of scattering of light is different.

Rainbows actually are in full circles. The center of that circle is the antisolar point. However, people standing on the ground can only see a part of the rainbow as the horizon blocks our other view. So, no one is able to see the complete circle of the rainbow from the ground. From aircraft, however, circular rainbows can be seen.

Reflection and Refraction inside the raindrop

The inside of a rainbow appears brighter than the outer part of the rainbow. This is because towards the edges, the rainbow colors overlap each other and hence a sheen of white light is produced. Only a part of the rainbow is in the form of visible light. Beyond the visible light of red color, infrared radiation exists while ultraviolet radiation exists beyond the light of violet color. Radio waves, x-rays, and gamma radiation also exist. These invisible parts of the rainbow are studied by scientists using an instrument known as the spectrometer.

Conditions for the Visibility of Rainbow

A person has to be at a certain angle with respect to the source of light i.e. the sun, in order to view a rainbow. The conditions for the visibility of a rainbow are:

• Water droplets must be present in the environment around the observer such as the presence of raindrops or fog.
• The person should be standing with their backs towards the sun.
• The arc of the rainbow will be more observable, the lower the sun is positioned in the sky. It should be placed at an angle less than 42 degrees in the sky.

Conditions to view rainbow in the sky

Double Rainbow

A double rainbow can be observed in the sky when the light from the sun undergoes reflection twice. It is a spectacular phenomenon that entails a faint secondary rainbow that appears just above the primary rainbow. 

Read More:  Newton's Universal Law of Gravitation and Gravitational Force

Due to the second reflection of light inside the raindrop, the spectrum of colors for the secondary rainbow in the sky gets reversed. Therefore, the red color appears in the inner section of the arch while the violet color is towards the outside. 

How to Make a Rainbow?

Isaac Newton discovered that white light consists of a spectrum of various colors that lie in the visible spectrum. Refraction is the process that splits the white light into multiple colors. Mainly, prisms were used to refract the visible light, however, water can also be used for the same purpose. We will use the concepts of density in the following experiment to form a rainbow in a jar. Are you ready to make some rainbows? Let us now look into the experiments that can help you make rainbows at home:

Rainbow Experiment 1

The aim of the experiment is to make use of the concepts of density to form a rainbow in a jar.

Material Required  

• One or two measuring spoons or tablespoon
• A cup of granulated sugar
• Food coloring tablets or food color of good quality
• A water container
• Five or six glasses

Procedure  

• Take five glasses and place them in a row.
• Add one tablespoon of sugar to the first glass.
• Then, in the first four glasses, add three tablespoons of sugar each.
• Continuing the procedure in the same way with a little difference, we now add two tablespoons of sugar to the second glass, three tablespoons to the third glass, and four tablespoons of sugar to the fourth glass.
• Now, stir all the glasses until the sugar completely dissolves.
• Then, add varying food colors to different glasses. 
• Pour one-fourth of the solution of glass four into glass five.
• Now, carefully pour the next layer of the solution in glass five from glass three.
• Be careful that the two layers don’t mix with each other. You can ensure the same by placing a spoon on the 1st layer and pouring the next mixture on the spoon in a gentle manner to avoid or at least minimize the splashes of color.
• Repeat the same procedure for the first and the second glass.

Read More:   Measurement of Time

Things to Keep in Mind  

• Pour the mixtures in the fifth glass gently. The more gentle and patient you are, the better results you will get.
• Ensure that the width of the mixtures you are pouring in glass five is the same for all the colors.

Result  

When different amounts of sugar are added to different glasses, a difference in density is created. You will observe that the layer at the bottom of the glass is the heaviest and the density varies for each layer that is placed on top of one another thereafter. Sooner or later, due to the concept of dynamics, the layers do mix with each other. However, if there is a greater difference in the density of the solutions, the phenomenon will last for a longer duration. 

Sugar-Water Density Experiment to form a rainbow

Rainbow Experiment 2 

The aim of the experiment is to make use of a glass prism to form a rainbow on a canvas or a sheet of white paper.

Read More:   Advanced Sunrise and Delayed Sunset

• Canvas or a white paper
• A glass prism
• Sunlight or a source of light
• Secure your canvas or the white paper with thumbtacks on a surface.
• Make sure the sheet is smooth and has no wrinkles so that the rainbow can appear nicely.
• Hold the glass prism in your hand in front of the paper capturing the sunlight.
• In the light beam, turn the prism around so that the light falls on the paper.
• The prism should be kept in the light beam so that the rainbow can be formed.
• The canvas or the paper should be laid in a flat and smooth manner without any creases.

The light will refract through the prism and we will observe a rainbow on the white paper. 

Formation of Rainbow with a Glass Prism

Rainbow Experiment 3

The aim of the experiment is to make use of a flashlight and a glass of water to form a rainbow.

• A clear glass filled with water.
• Flashlight emitting strong white light
• A piece of white paper
• With two pieces of the masking tape, cover the flashlight in a way that there is just a slit in the middle through which the light emits.
• Keep the glass of water ahead of the flashlight and shine the flashlight through it on a piece of white paper.
• You will be able to observe a rainbow on the white paper.

Things to keep in mind  

• The result and the colors of the rainbow will be observed in a better manner if the experiment is conducted in a dark room.
• You can shift the angle of light till you get a proper rainbow. 

You will be able to observe a spectrum of light on the white sheet of paper.

The light that is emitted from the flashlight i.e. the white light is formed of all the colours of the light (Red, Orange, Yellow, Green, Blue, Indigo, and Violet). When light is shined through the water, the light bends or undergoes refraction. It then splits into its seven constituent colors. The color is split because of the different wavelengths of different colors. 

Formation of Rainbow with a flashlight

Things to Remember

• Rainbow is a well-known optical phenomenon that leads to the formation of a glorious sight of a multicolor arc in the sky.
• Rainbow can be observed not only on rainy days but on sunny days too when one is near a fountain or a waterfall. 
• Rainbows are formed when sunlight, a white light, gets scattered by a droplet of water such as fog or raindrop by a process known as refraction.
• The colors with longer wavelengths are towards the red end of the spectrum while the shorter wavelengths have a blue or violet hue.
• A Rainbow is formed in the sky as a result of reflection, refraction, and the dispersion phenomenon of light in the water droplets.
• Using the concepts of varying densities of the solution, we can form a rainbow in a jar.
• With the help of a glass prism, we can observe the splitting of white light into different colors, also known as the process of dispersion which leads to the formation of rainbows.
• Each rainbow is unique in its aspect as each angle of scattering of light is different

Sample Questions

Ques. How are rainbows formed in the sky? (3 marks)

Ans. White light or sunlight is a mixture of lights of various wavelengths which are associated with different colors. When it passes from one medium of a definite density to another medium that is denser, the rays of the light bends. For instance, when light travels from air to water. This phenomenon of bending of light on traveling through a denser medium is known as refraction. The shorter the wavelength of light is, the more it bends. 

• When sunlight enters a droplet of water, it undergoes refraction.
• After entering the droplet, the ray of light is reflected back to the surface.
• The light ray again gets refracted when it leaves the droplet to reach our eye.

Hence, this is how a rainbow can be observed.

Ques. What are the conditions necessary to observe a rainbow? (3 marks)  

Ans. To see a rainbow, our backs must face the sun as the rainbow is only observed in the sky opposite to where the sun is. Amongst the spectrum of visible light, red color has the longest wavelength, hence it bends the least. The angle between the line of sight and incident light to observe red light is 42 degrees. Therefore, we can observe the color red at the very top of the rainbow.

As the violet color has the shortest wavelength, it bends the most. The angle between the line of sight and the incident light to observe violet is around 40 degrees. Therefore, the color violet appears at the bottom of the rainbow.

Ques. Why do rainbows seem arched? (3 marks)  

Ans. A rainbow can be observed when the angle between the incident light and the line of sight is between 40 to 42 degrees. Therefore, all the raindrops that produce the colors of the rainbow exist in a 3-D cone at whose tips our eyes exist. Therefore, the rainbows appear arched to us. The circular shape of the rainbows that exist below the ground is not visible to us. 

Ques. Why can’t we see the indigo color in the rainbow? (1 mark)  

Ans. Though indigo is a part of the spectrum of the rainbow, we are not able to see the color as our eyes are not sensitive to indigo color.

Ques. Is there an end to the rainbow? (2 marks)  

Ans. Rainbows are full circles spread over the entire sky, they have no end, and they extend even beyond the horizon. As the horizon blocks our view, we are only able to see a part of the rainbow. It is impossible to see the full circle. 

Ques. What are the 7 colors of a rainbow? (2 marks ) 

Ans. The acronym used to remember the order of the colors of the rainbow is VIBGYOR.

Ques. List down the conditions for the visibility of a rainbow. (3 marks)  

Ans. The conditions for the visibility of a rainbow are:

Ques. Do rainbows appear the same to everyone? (2 marks)  

Ans. No one sees the same rainbow as another person. This is because every person has a different antisolar point and each person views the rainbow from a different point and thus has a different horizon. Someone might see an extended rainbow where another person saw its end.

Ques. What are double rainbows? How are they formed? (3 marks)  

Ans. Many times a double rainbow can be observed by a person in the sky. This double rainbow phenomenon entails a faint secondary rainbow that appears just above the primary rainbow. 

The formation of these double rainbows takes place as the light reflects twice inside the rain droplet. Due to this second reflection, the spectrum of colors for the secondary rainbow in the sky gets reversed which means red color appears in the inner section of the arch of the rainbow while violet color is towards the outside. 

Ques. Can a rainbow be seen at night time? (3 marks)  

Ans. Yes, rainbows can be seen during the night time although it is a quite rare phenomenon. This is because the moon is bright enough to form a rainbow. However, since it is not nearly as bright as a sun, the rainbow that is formed by the moon is much fainter or weaker than a rainbow produced during the daytime by a sun. The night rainbow will also appear gray in color, this is due to the fact that our eyes see dim things and objects as black and white instead of seeing them in color.

CBSE X Related Questions

1. draw the structure of a neuron and explain its function., 2. balance the following chemical equations. (a) hno 3 +ca(oh) 2   \(→\)  ca(no 3 ) 2 + h 2 o  (b) naoh + h 2 so 4   \(→\)  na 2 so 4 + h 2 o  (c) nacl + agno 3   \(→\)  agcl + nano 3   (d) bacl + h 2 so 4   \(→\)  baso 4 + hcl, 3. what is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs, 4. how does phototropism occur in plants, 5. write the balanced chemical equations for the following reactions.  (a) calcium hydroxide + carbon dioxide  \(→\)  calcium carbonate + water  (b) zinc + silver nitrate  \(→\)  zinc nitrate + silver  (c) aluminium + copper chloride  \(→\)  aluminium chloride + copper  (d) barium chloride + potassium sulphate  \(→\)  barium sulphate + potassium chloride, 6. oil and fat containing food items are flushed with nitrogen. why, similar science concepts.

Exam Pattern

Paper Analysis

Mathematics Syllabus

Social Science Syllabus

Science Syllabus

Hindi Syllabus

English Syllabus

SUBSCRIBE TO OUR NEWS LETTER

• EO Explorer

• Global Maps

Notes from the Field

The arctic radiation-cloud-aerosol-surface interaction experiment (arcsix) in greenland.

May 25, 2024 Some 25 of us were up before 6 a.m. to head out on the bus from the hotel to Burlington International Airport to catch the C-130 aircraft, a military transport plane repurposed for NASA fieldwork, to begin our 7-hour flight to Pituffik.

Several mountains of baggage, including scientific instruments and personal luggage, separate us from the less-well-heated economy cabin, which was probably reserved for graduate students, though we are far too collegial a group to check seat assignments. As we head north and east, the landscape out the window is vast, entirely gray-scale, and unforgiving: sea ice with streaks and patches of open water as far as one can see in every direction.

About halfway through the flight, we cross the Arctic Circle. Here the scene is often reduced to pure gray, and one cannot tell what is sea ice, snow, or cloud. This is the challenge we have long faced when attempting to interpret our remote sensing imagery; now, as an early gift of the expedition, I experience it directly.

May 26, 2024

The site is halfway between Washington and Moscow. Most or all of the buildings were prefabricated, brought here by ship in the summer, and mounted on stilts due to the permafrost. Some rough grasses are the only apparent vegetation.

In some ways, the base is well appointed. There is a sports center with an abundance of every conceivable exercise machine, also a tanning machine and a perpetual pool, a huge gym, and a yoga room. There is a recreation center with a movie theater, a lounge area with free apples, tea, and coffee, a game room that is more like an arcade with multiple video machines, and a craft center that has sewing machines (including a state-of-the-art Serger), rock cutting and polishing machines, computer graphics, and printers.

This is a remote place. The site is protected by a thousand kilometers of ice in nearly all directions, and the only ways to get here are by air or by boat for a couple of months of the year, when the sea is not frozen. With full daylight all day and “night,” the times-of-day are marked only by artificial clocks; the natural ones are essentially absent.

May 27, 2024

This was mostly a flight-planning day, getting ready for the first science flight of the campaign. It turned cold, windy, and snow fell today. This was more like what I expected but didn’t experience during the first two days. But now it is sunny again, around 6 p.m., and near-freezing, so there is still standing water on the roadways, and we are past the season when it is safe to walk on the ice-bound bay. The severe environment calls for some specific adaptations.

For example, the outer doors have latches that seal upward, so a bear pushing down on the handle will be unable to open the door. The walkways are made of open steel grids, so snow and mud will drip through. Boots are to be brushed before entering buildings, and plastic boot covers are provided in an effort to limit the amount of dirt that is tracked in.

I took a late-night walk. It’s daylight anyway, though overcast, windy, cold, and flurrying. Pretty much what I expected here. 

The power went out twice today. Everything goes down, including the internet. I’m trying to keep everything charged, in case it happens again. Today’s weather represents “Condition Alpha” for storm warnings. That means just be on alert, in case things change. Condition Bravo means you cannot go outdoors without a buddy, or drive alone without a radio. Condition Charlie means you can’t walk out at all; there is a base taxi for urgent movement. Condition Delta: shelter in place. 

The pipes are all above-ground because of the freeze-thaw cycle that would destroy the pipes. I guess they must be heated and insulated. They cross the road by going overhead. 

Car and truck engines must be heated to avoid freezing and cracking. So, many of the buildings have power cords hanging out in front to run electric engine-block heaters. I didn’t take the last picture quite at midnight, but the scene doesn’t change much during the night.

I think I mentioned that it is mud season here. This is no joke. The place has a very industrial feel, and the only place to walk is on the mud roads. I’ve heard it will get worse as the mud deepens, and mosquitoes come out. Something to look forward to…

May 28, 2024

We had our first flight with the P3 today, and it was far better than I had expected. There was a rare case of cloud-free atmosphere over sea ice in one area north of Greenland where some buoys had been deployed, which allowed for both surface ice and aerosol characterization. Also, a nearly 3-hour run at ~500 feet captured aerosol properties over open water along the northern part of Baffin Bay. Among our objectives are learning the sources and properties of aerosols in the Arctic, their evolution as they age, and their impact on clouds. Others are especially interested in the properties of sea ice as it melts. So, this gives us a start on those objectives.

May 29, 2024

The wind is a force of nature. Today it has been blowing at something like 40 miles per hour, with gusts considerably higher. It literally takes your breath away—and this is just Condition Alpha. 

Gusts create the sensation of blowing you away. All this under a relatively clear sky, bright sun, just a few clouds. It is somewhat other-worldly to one who has lived a life at lower latitudes. The temperature is only a few degrees below freezing, but the weather today gives new meaning to the term “wind chill.” 

June 1, 2024

Today was an official day off, and in particular, a mental health day for the forecasters. Several of the military folks on the base arranged to take a group of us on a hike over the Greenland Ice Cap. There were 15 of us in five trucks. The trip involved a fair amount of driving on gravel roads in trucks—about half the time driving, half hiking – 5 hours total. The hike itself was about 5 or 6 miles, and we walked around and then on the glacier, though we never did find the Starbucks.

In addition to the stark beauty of the rock fields and ice, the sky is unlike anything we normally see at lower latitudes. The surface is cold, and the atmosphere is no colder (and sometimes is even warmer) than the surface, i.e., it is stably stratified—the “warm” air is already up, so there is not a lot of warm air rising and mixing that typically happens when the surface is heated directly by the Sun.

The glaciers have brought an enormous diversity of stones that litter the ground, and every piece of wood here was carried in from somewhere else. There are little clumps of vegetation, just enough to satisfy the appetites of musk oxen. 

So far, I’ve seen Arctic fox (no pictures—they disappeared too quickly), musk ox in the distance, Arctic hare, and snow goose. No polar bears—and no complaints about that. 

June 7, 2024

This evening I took a long walk out to the ice-bound pier… AND I SAW AN OTTER!!!

June 4, 2024

The Arctic foxes are molting. They were very cute when their coats were all white. Now they are losing their winter coats and turning brown. I did see a couple of full white coats, but was too slow to get a photo. 

June 8, 2024

The project rented a van, and ten of us went off to climb the Dundas, that imposing rock feature not far from the base, though to get there without walking on thin ice (here the term is not merely a metaphor), one has to drive about 30 minutes over rocky and sometimes quite steep roads around the frozen bay.

The angle of repose is the angle a pile of dry sand (or salt) will make if you dump a bucket of it on the ground. It is generally steep (depends in part on the grain size and shape of the sand particles). Dundas is about 725 feet high; it appears to be the remnant of a glacial moraine—rock pushed here by an advancing ice sheet at least that high, that remained after the ice melted away. It is loose sand and rock, mostly gravel and cobble-sized. The climb up was, frankly, arduous, as there are not a lot of footholds. 

The first part was steep enough that going on all fours was necessary in places, and the sand and small rocks would slip easily down the slope as one persevered upward. The final part was up a sheer rock wall that was graced, mercifully, with a sturdy rope. My pictures are lacking for the entire traverse, as all my effort went into the climb itself. I did stop part way up the rock wall to check my life insurance policy.

 The view from the top was spectacular, but truthfully, there are so many great vistas in this rugged place that the main reward was accomplishing the ascent itself. 

The way down was similarly fraught, except that below the rock wall, I had pretty much no choice but to slide down bit by bit—the loose surface material would give way at every step. So, on my back, lift up my rear, slide a few feet using my boots to stop, and repeat. There was some interesting vegetation on the slope—tiny plants and lichen, which I did photograph. I’m told that some of these plants can be hundreds of years old. 

In the distance, we saw some dark spots that the binoculars suggested were seals. (Oh, yes—someone here said that my otter from last night was actually a ring seal; not sure that is authoritative, but…).

June 9, 2024

I agreed to join this afternoon’s walk up the edge of the Greenland Ice Sheet. 

The slope is moderate by Dundas standards, and the path is completely snow-covered. The walk up is of course uphill, and a steady wind of 30–40 mph (the katabatic wind), with significantly higher gusts, blows off the ice. This guaranteed that however far we got up the ice sheet, we would certainly be able to make it down, either on foot or airborne.

There were pools of water within ice basins at the base. They look a beautiful shade of blue. We saw this in Alaska as well. I think it must be that ice either absorbs all the longer wavelengths, or it preferentially scatters blue, or both. The optics here are stunning, at least to me. Probably because they are unfamiliar. 

One way painters provide a sense of distance in a painting is with “atmospherics,” that is, they increasingly blur the edges of more distant objects to account for light scattering by atmospheric gas and aerosols. Mountain climbers experience the opposite, in the thinner atmosphere, remote objects are sharper than they would in everyday experience, so more distant objects appear closer than they actually are. This is true here in Greenland as well, though we are not at a very high elevation along the coast. I expect the phenomenon in this case is due to a very clean atmosphere. 

June 11, 2024 Today I got to fly on the P-3. Every satellite scientist should be required to take at least one such flight to see what the Earth is really like. We flew across northern Greenland and over sea ice. In the two weeks since the campaign deployment began, the depth of the sea ice, and the snow upon it, both decreased at those buoys (where it was measured), and, of course, most everywhere else as well.

A field campaign is a layered operation. Aircraft flight scientists build, run, and maintain the twenty or so instruments that measure particle composition, gas concentration, cloud properties, surface reflectivity, and upwelling and downwelling energy. They are awake by 4 a.m. to prepare their instruments for flight, worry about power supplies and calibration, then sit on the plane for six or seven hours, noting what they see from their measurements and out the window.

The number of leads (i.e., openings in the ice) has increased in places. We flew at high elevation to survey the area, measure the overall surface topography and reflectance, and sample aerosol layers aloft, then descended to 300 feet above the ice to capture aerosols emanating from the surface. The photos tell an accessible part of the story. The rest must be teased out of the data in the coming months and years. But my ride is over for now—there is an aerosol forecast due tomorrow.

June 12, 2024

It was flurrying this evening, and my walk carried me down toward the pier. But you might be pleased to know, I did not go all the way; several seals have now been seen on the ice at the pier. My otter or seal in the water was the first anyone saw, and although they say it is relatively rare for bears to go near the base, seals are their primary food. I figured, after a long winter hibernation, a bear might not count me as even a light snack, but in consideration that I had already booked my flight home, I turned around before getting very near the water’s edge. 

June 14, 2024

I should say that the food here is okay. Better than I expected. Of course, in such circumstances, it pays to begin with low expectations: hardtack, pemmican, and beef jerky. The cafeteria serves a lot of beef and pork, but there is also chicken, a reasonable salad bar, excellent, fresh bread (the highlight in my opinion), always two of THE three kinds of fruit (apples, oranges, and bananas—so yes, they mix apples and oranges), and of course, Danish, at least in the morning. 

In the evening I took a walk, as usual, and ended up in one of the dozens of prefab buildings on the base, with the suggestive label “Heritage Hall.” The door was not locked, and the lights turned on as you entered each room. The place is a sort of museum, a repository for things discarded from the 1950s and 60s.

They have a computer punch-card machine, a vacuum-tube TV set, and a radar scope you will recognize from science-fiction movies. Also some notebooks with photos of the army’s Camp Tuto (now abandoned—only remnants of the airfield remain) and the presumptive city “Camp Century” they built into the ice in the 1950s. The walls flowed at glacial speed but ultimately collapsed.

Thule base was established in 1951, succeeding three waves of Inuit who inhabited the area, apparently beginning 4,500 years ago. The most recent came around 900 CE, met the Norse about 100 years later, and were moved to a new village 60 miles to the north in 1953. There is even a Life Magazine cover showing ships delivering material to the base in September 1952. 

Ralph Kahn , an emeritus research scientist at NASA’s Goddard Space Flight Center now at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder, spent three weeks at Pituffik Space Base in northern Greenland in the summer of 2024. He was one of dozens of scientists who participated in ARCSIX ( Arctic Radiation-Cloud Aerosol-Surface Interaction Experiment ), a NASA-sponsored field campaign that made detailed observations of clouds and atmospheric particles to better understand the processes that affect the seasonal melting of Arctic sea ice. These excerpts from his emails home to family provide a glimpse of what life was like on one of the world’s most northern scientific outposts in the world. Photos were taken by Kahn or Gary Banzinger, a NASA videographer who also participated in the campaign. Kahn, an atmospheric scientist, worked with colleagues to provide daily aerosol forecasts that were used to help plan flights.

Tags: aerosols , climate change , clouds , Greenland , ice , NASA , sea ice

This entry was posted on Friday, August 23rd, 2024 at 3:40 pm and is filed under Arctic Radiation Cloud Aerosol Surface Interaction Experiment (ARCSIX) . You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

Comments are closed.

Browse by Expedition

• A Satellite Scientist Visits the Ice, Alaska 2016
• African Blue Carbon Systems
• AfriSAR in Gabon 2016
• Airborne Lunar Spectral Irradiance Instrument (air-LUSI)
• Arctic Radiation Cloud Aerosol Surface Interaction Experiment (ARCSIX)
• Arctic-Boreal Vulnerability Experiment (ABoVE)
• ATom: World Survey of the Atmosphere
• Balloons for Science
• Beaufort Gyre Exploration Project 2016: Searching for Sea Ice
• Connecting Space to Village
• Cyclone Global Navigation Satellite System (CYGNSS)
• Dual-channel Extreme Ultraviolet Continuum Experiment (DEUCE)
• Eco3D: Exploring the Third Dimension of Forest Carbon
• Global Hawk Pacific (GLOPAC)
• GO-SHIP 2017
• Goddard Instrument Field Team (GIFT)
• GPM in Japan, the Road to Launch
• Greenland Aquifer Expedition
• Greenland Surface Melt Study 2013
• Hurricane and Severe Storm Sentinel (HS3) 2014
• ICESat-2 Antarctic Traverse
• International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic Winter Games (ICE-POP)
• Iowa Flood Studies
• Journey to Galapagos
• Landsat 8 Launch 2013
• LARGE (The Langley Aerosol Research Group Experiment) 2014
• Leaf to Landscape
• MABEL: Spring 2011
• NAAMES (North Atlantic Aerosols and Marine Ecosystems Study)
• Nansen Ice Shelf, Antarctica 2015
• NASA Agriculture
• NASA in Alaska
• North Woods, Maine 2009
• Oceans Melting Greenland (OMG)
• Olympic Mountains Experiment (OLYMPEX) 2015
• Operation IceBridge
• Operation IceBridge: Antarctic 2013
• Operation IceBridge: Antarctic 2014
• Operation IceBridge: Antarctic 2017
• Operation IceBridge: Arctic 2011
• PACE: Color of the Ocean and Blue Sky
• Pine Island Glacier 2011
• Real-time Observations of Greenland's Under-ice Environment (ROGUE)
• Salinity Processes in the Upper Ocean Regional Study (SPURS)
• Sea to Space Particle Investigation
• SEAT: Satellite Era Accumulation Traverse
• Ship-Aircraft Bio-Optical Research (SABOR)
• Siberia 2012 – Embenchime River Expedition
• Soil Moisture Active Passive (SMAP)
• South Pacific Bio-optics Cruise 2014
• SWESARR: NASA’s Newest Snow Instrument
• The Ablation Zone: Where Ice Goes to Die
• The Uphill Road to Measuring Snow
• The Western Siberia Expedition 2010
• Uncategorized
• Urban Aerosols: Who CARES?
• VISIONS-2: Imaging Earth’s Portal to Space

Browse by Date

• Entries (RSS)
• Comments (RSS)

• Environment

Rubio, Scott call fast-tracking of Florida state park golf course plan ‘ridiculous’

• Max Chesnes Times staff
• Emily L. Mahoney Times staff

In a scathing letter to Gov. Ron DeSantis Friday, Republican U.S. Senators Marco Rubio and Rick Scott joined local officials in criticizing the rushed process behind state plans to develop golf courses on Jonathan Dickinson State Park on Florida’s Atlantic coast.

The officials called a scheduled one-hour hearing at 3 p.m. Tuesday for the public to weigh in “absolutely ridiculous,” adding that “not one” member of a state committee that is responsible for voting on the plan would attend the meeting to hear the public’s concerns.

The Florida Department of Environmental Protection planned to hold near-simultaneous meetings around the state Tuesday afternoon for the public to comment on its designs to add golf courses, 350-room lodges, pickleball courts, disc golf courses and more to nine state parks. After these meetings, a state committee called the Acquisition and Restoration Council would have voted on whether to move forward.

“We believe every voting member of the (Acquisition and Restoration Council) must attend a public comment meeting before taking any action regarding the proposal,” the letter reads. “An hour-long meeting on a weekday afternoon when most people are at work will not suffice.”

Hours after the letter was released, the department posted on social media that it would be postponing all the public meetings about the state park plans.

“Due to the overwhelming interest with the 2024-25 Great Outdoors Initiative, (the Department of Environmental Protection) is looking for new venues to accommodate the public,” the agency wrote on X. It said new meeting dates would be announced soon, most likely for the week of Sept. 2.

The letter from Scott, Rubio and other officials focused primarily on the process for allowing the public to weigh in on the proposal at Jonathan Dickinson rather than comment more broadly on the DeSantis administration’s designs for amenities in nine parks total. Since they were revealed earlier this week, the plans have brought an unusually swift and crushing wave of bipartisan blowback.

While the DeSantis administration has doubled down on the proposal, it said Friday that officials would ensure better opportunities for public input. Its social media post included a link for a website where Floridians can submit suggestions on the plans.

Due to the overwhelming interest with the 2024-25 Great Outdoors Initiative, DEP is looking for new venues to accommodate the public. We want to ensure everyone has the opportunity to participate. Public input is vital to DEP decision-making. To gather feedback on your favorite… pic.twitter.com/duFLtY3mNg — Florida DEP News (@FLDEPNews) August 23, 2024

Jonathan Dickinson is home to the largest amount of protected scrub-jay habitat in Southeast Florida. The Department of Environmental Protection has said it would “minimize” the impact to sensitive habitats. It posted on social media Friday that one of the pickleball courts in Broward County’s Dr. Von D. Mizell-Eula Johnson State Park would be built on land that’s already a parking lot.

Keep up with Tampa Bay’s top headlines

Subscribe to our free DayStarter newsletter

You’re all signed up!

Want more of our free, weekly newsletters in your inbox? Let’s get started.

In the Tampa Bay area, Hillsborough River State Park and Pinellas’ Honeymoon Island are also slated to get pickleball courts.

Jeremy Redfern, a DeSantis spokesperson, has said that the additional amenities would make the parks “more accessible to the public.”

This is not Sen. Scott’s first brush with public outrage on this topic. In 2011, when Scott was governor, he played a role in a similar plan to build golf courses on state parks, the Tampa Bay Times reported at the time. Proposed legislation had reportedly emerged after discussions between golfer Jack Nicklaus and Scott, Nicklaus’ lobbyist said then.

In a statement to the Times, Nicklaus Companies and Nicklaus Design said they have no involvement in any current proposals.

The letter demanded two meetings, one in Stuart and one in Jupiter, “both for as long as it takes to hear all concerns.” It suggested holding them after Thanksgiving, when more part-time residents will be in Florida for the winter, to give the process more “credibility.”

U.S. Rep. Brian Mast, R-Stuart, who represents the district that includes Jonathan Dickinson State Park, also signed on to the letter. Earlier this week, Mast urged voting members of the Acquisition and Restoration Council to attend the public meeting scheduled for Tuesday so they could be eye-to-eye with the residents affected by the proposed development. In a phone interview Friday, Mast said he had yet to hear a response from a single council member.

“They’re going to try and develop something without disturbing it? How about they just don’t disturb it,” Mast said.

In addition to Scott, Rubio and Mast, 12 other Treasure Coast officials signed the letter, including state Sen. Gayle Harrell, Reps. Toby Overdorf and John Snyder, and county commissioners from Martin and Palm Beach counties.

Max Chesnes is an environment and climate reporter, covering water quality, environmental justice and wildlife. Reach him at [email protected].

Emily L. Mahoney is the energy reporter. Reach her at [email protected].

MORE FOR YOU

• Advertisement

ONLY AVAILABLE FOR SUBSCRIBERS

The Tampa Bay Times e-Newspaper is a digital replica of the printed paper seven days a week that is available to read on desktop, mobile, and our app for subscribers only. To enjoy the e-Newspaper every day, please subscribe.