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Castor oil‐based polyurethane has been researched for its utility in heavy metal adsorption. To improve the adsorptive performance, the polymer can be incorporated with cellulose—a renewable and widely available biopolymer. The aim of this research was to synthesize a film composite prepared from castor oil‐based polyurethane and cellulose for adsorptive removal of aqueous Cd and Pb. One‐shoot synthesis method was employed by mixing cellulose filler with castor oil and toluene diisocyanate (TDI). Characterization was carried out by FT‐IR, SEM, TGA, DSC, and contact angle analyses. Batch adsorption was carried out for the Cd and Pb with variations in contact time and initial pH, before analyzed for the adsorptive performance using 1064 nm Nd:YAG laser spectroscopy. The resulted adsorbents had improved thermal stability, and lower hydrophobicity. Adsorption of Pb and Cd increased 2 and 35 times after the addition of 0.1 g cellulose, respectively. Batch adsorption test revealed that the optimum conditions are 120‐min contact time and pH of 9 and 7 (for Cd and Pb, respectively). In conclusion, incorporation of cellulose could modify the characteristics of castor oil‐based polyurethane film and improve the adsorption of Cd and Pb. [ABSTRACT FROM AUTHOR]

Three novel phenolic compounds were isolated from the heartwood of Millettia pendula along with eight known compounds. Among the known compounds, six were isolated from this species for the first time. Structural determination of the isolated compounds was accomplished using 1D and 2D nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Two of the isolated compounds, 2 and 6, showed red and purple pigmentation, respectively. These compounds contained a conjugated π system composed of benzofuran and p-benzoquinone moieties. We therefore hypothesize that a hydroquinone moiety, present in precursors of 2 and 6, is autoxidized by activated oxygen in the air to form p-benzoquinone. The difference in colors between these two compounds was due to the difference in the B ring substituents. Expansion of their conjugated pi systems allows 2 and 6 to absorb and reflect light in the visible region, and results in the characteristic purple coloring of M.pendula. [ABSTRACT FROM AUTHOR]

Using chemical activation techniques at dissimilar carbonization temperatures, activated carbon adsorbents were produced from Palmyra palm fruit biomass in this work. X‐ray diffraction, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, laser Raman spectroscopy, scanning electron microscopy, CHNS‐elemental analysis, and N2 adsorption studies were among the characterization techniques used to assess the characteristics of the carbon adsorbents. The carbon adsorbents from Palmyra palm fruit were used to absorb CO2 in a temperature range of 25–70°C. The findings of the characterization showed that these carbons have a large surface area and microporosity. The temperature of carbonization and the activating agent had an impact on the surface characteristics. The samples with the highest adsorption capacity, 4.70 mmol/g at 25°C, were the activated carbons made by treating them with KOH and then carbonizing them at 750°C. The physicochemical properties of the adsorbents provided an explanation for their high adsorption capacity. The adsorbents showed simple desorption and maintained constant activity during ten cycles of recycling. [ABSTRACT FROM AUTHOR]

Silicon‐based on‐chip broadband surface‐enhanced infrared absorption (SEIRA) is highly desired for integrated micromolecular detection systems, taking advantages of CMOS mass production, low cost, high sensitivity, etc. However, the silicon platform is difficult to operate in the mid‐infrared wavelength region above 4 µm where abundant fingerprint characteristics of biomolecules are located, because of the strong absorptions in silicon dioxide cladding above 4 µm. Here, a large‐core rib silicon waveguide‐integrated gradient nanoantenna array is proposed for broadband long‐wave infrared biomolecular detection. It is shown that Low loss propagation of light in the long‐wave infrared region up to 7 µm (1428 cm−1) in silicon photonics can be achieved while avoiding complex fabrication techniques. A gradient nanoantenna array is designed on the waveguide to achieve broadband enhancement from 5 to 7 µm (1428–2000 cm−1). Laser spectroscopy of bovine serum albumin on the chip is demonstrated, showing enhancement of absorbance by approximately ten times over laser transmission spectroscopy in the amide bands. Such a platform opens up a new horizon of silicon‐based on‐chip SEIRA biomolecular detection. [ABSTRACT FROM AUTHOR]

The results of laser spectroscopy experiments of antiprotonic helium atoms carried out at the Antiproton Decelerator of CERN, and pionic helium atoms measured at the 590MeV ring cyclotron facility of the Paul Scherrer Institute are reviewed. The former experiment determined the antiproton-to-electron mass ratio as Mp¯/me=1836.1526734(15). In the latter, a resonant transition (n,ℓ)=(17,16)→(17,15) of pionic helium at a frequency of ν≈183760GHz was detected. Some future perspectives are briefly described. [ABSTRACT FROM AUTHOR]

In this article, the corrosion resistance of a cobalt–chromium‐based laser cladding reinforced with different microparticles: boron nitride, graphene oxide, and graphite, added for increased tribological performance, is explored. Samples are fabricated by premixing cobalt–chromium powder with microparticle additions and cladding onto 316L stainless steel base metal. The corrosion behavior is measured in industrially relevant applications: 1 m acetic acid and 3.5 wt% NaCl, using open‐circuit potential, electrochemical impedance spectroscopy, linear polarization resistance, and cyclic polarization. Laser ablation–inductively coupled plasma–mass spectrometry is used to analyze the distribution of the chemical elements throughout the coatings. The reference cladding's corrosion resistance is outstanding in both electrolytes, with a corrosion rate (CR) of ≤0.19 μm year−1 and no pitting tendencies. With the addition of microparticles, the claddings maintain their remarkable pitting resistance, but show an increase in CR up to 0.98 μm year−1 due to the nonuniform distribution of the microparticles into the matrix. [ABSTRACT FROM AUTHOR]

In this study, we developed and validated an improved tuning method for a nonlinear scanning laser diode in methane gas sensing, using wavelength modulation spectroscopy - tunable diode laser absorption spectroscopy (WMS-TDLAS). This approach combines cubic nonlinear scanning with high-frequency modulation to precisely target the methane absorption peak at 6046.96 cm−1. The method enhances absorption time, thus increasing system sensitivity and stability. Our results show that this nonlinear scanning, optimized for peak absorption, significantly improves the slope of the methane concentration relationship curve by 76.9%. It also reduces the standard deviation by 61.1% and the limit of detection by 60% compared to linear scanning. The limit of detection the system is 4.2 ppm, and the optimal integration time is 48s. This novel modulation strategy significantly enhances the WMS-TDLAS system's efficiency, offering significant benefits for various applications. • Cubic nonlinear scanning method (CNSM) was proposed and CH 4 detection was verified. • Scanning central wavenumber of LD obtained a longer absorption time. • CNSM significantly improved the slope of the methane concentration curve. • The sensing sensitivity and stability were improved by 45% and 49%, respectively. [ABSTRACT FROM AUTHOR]

In this study we introduce photoluminescence analysis of nano powder YAlO3 doped with Er3+ and Yb3+. We compare this material with other hosts, Gd2O3, CaGdAlO4 and Y2O2S, doped with Er3+ and Yb3+. Beside usual ways to characterize these materials we also include visual comparison by data dimensionality reduction techniques, as a way for initial assessment of a new material. Samples were excited at 980 nm by using pulsed laser diode to analyze effects of host matrices on optical emission of erbium. For this purpose the luminescence spectra of all samples were obtained in a continuous series of measurements under the same experimental conditions. Moreover, the samples were prepared in the same way, by combustion synthesis. We compare the possibilities of using these materials for remote temperature sensing, showing that YAlO3:Er3+, Yb3+ is a good candidate for remote temperature sensing. [ABSTRACT FROM AUTHOR]

A new optical diagnostic method that predicts the global fuel–air equivalence ratio of a swirl combustor using absorption spectra from only three optical paths is proposed here. Under normal operation, the global equivalence ratio and total flow rate determine the temperature and concentration fields of the combustor, which subsequently determine the absorption spectra of any combustion species. Therefore, spectra, as the fingerprint for a produced combustion field, were employed to predict the global equivalence ratio, one of the key operational parameters, in this study. Specifically, absorption spectra of water vapor at wavenumbers around 7444.36, 7185.6, and 6805.6 cm–1 measured at three different downstream locations of the combustor were used to predict the global equivalence ratio. As it is difficult to find analytical relationships between the spectra and produced combustion fields, a predictive model was a data-driven acquisition. The absorption spectra as an input were first feature-extracted through stacked convolutional autoencoders and then a dense neural network was used for regression prediction between the feature scores and the global equivalence ratio. The model could predict the equivalence ratio with an absolute error of ±0.025 with a probability of 96%, and a gradient-weighted regression activation mapping analysis revealed that the model leverages not only the peak intensities but also the variations in the shape of absorption lines for its predictions. [ABSTRACT FROM AUTHOR]

Carbonate minerals are globally distributed on the modern and ancient Earth and are abundant in terrestrial and marine depositional environments. Fluid inclusions hosted by calcite retain primary signatures of the source fluid geochemistry at the time of mineral formation (i.e., pCO2) and can be used to reconstruct paleoenvironments. Confocal laser Raman spectroscopy provides a quick, nondestructive approach to measuring the constituents of fluid inclusions in carbonates and is a reliable method for qualitatively determining composition in both the aqueous and gas phases. Here, we demonstrate a method for accurately quantifying bicarbonate and carbonate ion concentrations (down to 20 mM) and pH (7–11) from calcite fluid inclusions using confocal Raman spectroscopy. Instrument calibrations for carbonate (CO32–) and bicarbonate (HCO3–) concentrations and pH were performed using stock solutions. We show that the calcite host mineral does not affect the accurate quantification of carbonate solution concentrations and that these parameters can be used to estimate the pH and pCO2 of a solution entrapped within a fluid inclusion. We apply the technique to Icelandic spar calcite and find a [CO32–] = 0.11, [HCO3–] = 0.17, pH = 10.1, and CO2 parts per million = 2217. The presence of gaseous Raman bands for CO2, CH4, and H2S suggests that the mineral precipitated in a reducing environment. [ABSTRACT FROM AUTHOR]

This study investigates the optical properties of diffraction gratings using localized surface plasmon resonance (LSPR) with metal nano-hemispheres. We fabricated metal nano-hemisphere gratings (MNHGS) with Ga, Ag, and Au and examined their wavelength-selective diffraction properties. Our findings show that these gratings exhibit peak diffraction efficiencies at 300 nm, 500 nm, and 570 nm, respectively, corresponding to the LSPR wavelengths of each metal. The MNHGs were created through thermal nanoimprint and metal deposition, followed by annealing. The experimental and simulation results confirmed that the MNHGs selectively diffract light at their resonance wavelengths. Applying these findings to third-order nonlinear laser spectroscopy (MPT-TG method) enhances measurement sensitivity by reducing background noise through the selective diffraction of pump light while transmitting probe light. This innovation promises a highly sensitive method for observing subtle optical phenomena, enhancing the capabilities of nonlinear laser spectroscopy. [ABSTRACT FROM AUTHOR]

Δ (17 O) measurements of atmospheric CO 2 have the potential to be a tracer for gross primary production and stratosphere–troposphere mixing. A positive Δ (17 O) originates from intrusions of stratospheric CO 2 , whereas values close to -0.21‰ result from the equilibration of CO 2 and water, which predominantly happens inside plants. The stratospheric source of CO 2 with high Δ (17 O) is, however, not well defined in the current models. More, and long-term, atmospheric measurements are needed to improve this. We present records of the Δ (17 O) of atmospheric CO 2 obtained with laser absorption spectroscopy from Lutjewad in the Netherlands (53°24 ′ N, 6°21 ′ E) and Mace Head in Ireland (53°20 ′ N, 9°54 ′ W) that cover the period 2017–2022. The records are compared with a 3-D model simulation, and we study potential model improvements. Both records show significant interannual variability of up to 0.3 ‰. The total range covered by smoothed monthly averages from the Lutjewad record is -0.34‰ to -0.12‰ , which is significantly higher than the range of -0.20‰ to -0.17‰ for the model simulation. The 100 hPa 60–90° N monthly-mean temperature anomaly was used as a proxy to scale stratospheric downwelling in the model. This strongly improves the correlation coefficient of the simulated and observed year-to-year Δ (17 O) variations over the period 2019–2021 from 0.40 to 0.82. As the Δ (17 O) of atmospheric CO 2 seems to be dominated by stratospheric influx, its use as a tracer for stratosphere–troposphere exchange should be further investigated. [ABSTRACT FROM AUTHOR]

Global energy consumption is increasing yearly, yet the world is trying to move toward carbon neutrality to mitigate global warming. More research is being done on energy storage devices to advance these efforts. One well‐known and widely studied technology is Zn‐ion batteries (ZIBs). Therefore, this paper demonstrates how laser irradiation at wavelengths of 266 and 1064 nm, in the presence of air or water, can enhance the electrochemical performance of metallic zinc anode in alkaline electrolyte. The obtained samples are characterized using X‐ray diffraction analysis, scanning electron microscopy, and Raman spectroscopy. Then, the electrochemical properties are studied by cyclic voltammetry and impedance measurements. Results indicate that the laser processing of the Zn sample increases surface‐specific capacity by up to 30% compared to the non‐irradiated Zn sample. Furthermore, electrochemical measurements reveal enhanced participation of metallic Zn grains in the oxidation and reduction processes in irradiated samples. In future research, integrating laser treatment into electrode preparation processes can become essential for optimizing anode battery materials. [ABSTRACT FROM AUTHOR]

A highly efficient and sensitive ion mobility spectrometry (IMS) system with laser desorption sampling was applied for rapid explosive detection using different surface materials. This portable IMS detector, powered by a battery, offers mobility and is suitable for use in the field or combat zones. The laser desorption (LD) sampling of common explosives (Trinitrotoluene—TNT; Dinitrotoluenes—DNTs; Hexogene—RDX; pentaerythritol tetranitrate—PETN; plastic explosives—Compound 4 (C-4) and Semtex) on a wide range of common surface materials, such as metal, ceramic, plastic, glass, drywall, paper, wood, and textiles, was studied. Successful detection was achieved on nearly all surfaces except flammable materials (paper, wood, and textiles). The limit of detection (LOD) was determined for each explosive and specific surface, demonstrating an impressive LOD of 7 ng/mm2 for TNT. RDX, C-4, PETN, and Semtex achieved LOD values of 15 ng/mm2, while DNTs showed an LOD of approximately 50 ng/mm2. [ABSTRACT FROM AUTHOR]

Standoff laser absorption spectroscopy (LAS) has attracted considerable interest across many applications for environmental safety. Herein, we propose an anodic aluminum oxide (AAO) microcantilever LAS combined with machine learning (ML) for sensitive and selective standoff discrimination of explosive residues. A nanoporous AAO microcantilever with a thickness of <1 μm was fabricated using a micromachining process; its spring constant (18.95 mN/m) was approximately one-third of that of a typical Si microcantilever (53.41 mN/m) with the same dimensions. The standoff infrared (IR) spectra of pentaerythritol tetranitrate, cyclotrimethylene trinitramine, and trinitrotoluene were measured using our AAO microcantilever LAS over a wide range of wavelengths, and they closely matched the spectra obtained using standard Fourier transform infrared spectroscopy. The standoff IR spectra were fed into ML models, such as kernel extreme learning machines (KELMs), support vector machines (SVMs), random forest (RF), and backpropagation neural networks (BPNNs). Among these four ML models, the kernel-based ML models (KELM and SVM) were found to be efficient learning models able to satisfy both a high prediction accuracy (KELM: 94.4%, SVM: 95.8%) and short hyperparameter optimization time (KELM: 5.9 s, SVM: 7.6 s). Thus, the AAO microcantilever LAS with kernel-based learners could emerge as an efficient sensing method for safety monitoring. [ABSTRACT FROM AUTHOR]

Ultrafast spectroscopy can be used to study dynamic processes on femtosecond to nanosecond timescales, but is typically used for photoinduced processes. Several materials can induce ultrafast temperature rises upon absorption of femtosecond laser pulses, in principle allowing to study thermally activated processes, such as (catalytic) reactions, phase transitions, and conformational changes. Gold–silica core–shell nanoparticles are particularly interesting for this, as they can be used in a wide range of media and are chemically inert. Here we computationally model the temporal and spatial temperature profiles of gold nanoparticles with and without silica shell in liquid and gas media. Fast rises in temperature within tens of picoseconds are always observed. This is fast enough to study many of the aforementioned processes. We also validate our results experimentally using a poly(urethane‐urea) exhibiting a temperature‐dependent hydrogen bonding network, which shows local temperatures above 90 °C are reached on this timescale. Moreover, this experiment shows the hydrogen bond breaking in such polymers occurs within tens of picoseconds. [ABSTRACT FROM AUTHOR]

Optical fiber sensor emerges as a highly promising technology for trace gas detection due to their high sensitivity, remote capability, and immunity to electromagnetic interference. However, the state‐or‐the‐art fiber‐optic gas sensors typically use lengthy optical fibers as gas absorption cells or coatings with functional materials to achieve more sensitive gas detection, which poses challenges such as slow response and/or poor selectivity, as well as limitations on their use in confined spaces. Here, an ultraminiature optical fiber‐tip photothermal gas sensor via direct 3D micro‐printing of a Fabry‐Pérot cavity on the end face of a standard single‐mode optical fiber is reported. It enables not only direct interaction between light and gas molecules at the fiber output but also remote interrogation through an interferometric read‐out scheme. With a low‐finesse microcavity of 66 µm in length, a noise equivalent concentration of 160 parts‐per‐billion acetylene gas is demonstrated with an ultra‐fast response time of 0.5 s. Such a small high‐performance photothermal gas sensor offers an approach to remotely detecting trace gases for a myriad of applications ranging from in‐reactor monitoring to medical diagnosis. [ABSTRACT FROM AUTHOR]

The influence of interatomic collisions in a gaseous medium on intra-Doppler resonances of absorption of optical radiation in a thin gas cell was theoretically studied and could be recorded by recently developed laser spectroscopy methods. The limitations on the pressure of the gaseous medium at which the influence of such collisions on the width of these resonances was insignificant were determined. The results could find application in ultra-high resolution atomic spectroscopy and in compact optical frequency standards based on the thin gas cells under consideration. [ABSTRACT FROM AUTHOR]

The photoprocesses of diethylamino derivatives of 1,4- and 1,3-distyrylbenzenes in MeCN were studied using absorption, luminescence, 1H NMR, and laser kinetic spectroscopy. Compounds 1 and 2 undergo intersystem crossing to the triplet state and exhibit delayed fluorescence. It was concluded that dye radical anions and radical cations are formed upon dismutation of the triplet state in the presence of an electron donor or acceptor. Quantum mechanical calculations for the structures of diethylamino distyrylbenzenes in the ground and excited states were carried out, making it possible to establish the structures of isomers and the most stable conformers for both compounds. [ABSTRACT FROM AUTHOR]

In this work, cellulose was effectively produced from corn husks by a simple and eco‐friendly method. Major influencing variables for cellulose extraction were examined, and the highest yield of lignin and hemicellulose cleavage was achieved after corn husks were treated in 12.5 wt % NaOH solution at solid/liquid ratio (S/L) of 1:10 g mL−1, 70 °C for 90 min. Subsequent bleaching conducted in 10 wt % H2O2 solution at 80 °C for 90 min produced cellulose with a lightness value (L*) of ∼87, chromaticity indexes a* = −1.85, b* = 2.94 with high purity, 90.86 %, and crystallinity, 64.94 %. Fourier transform infrared, scanning electron microscopy, and x‐ray diffraction analysis showed a clear transition in morphology, structure modification, and crystallinity consistent with the alteration of the chemical composition from raw material to delignified residue and the bleached one. To synthesize microcrystalline cellulose (MCC), the hydrolysis was investigated in H2SO4 solutions of different concentrations and durations via monitoring particle size distribution by laser diffraction spectroscopy. At the most efficient conditions (30 wt % H2SO4, 18 h, 45 °C, 1:10 S/L ratio), the obtained MCC reached an average particle size of 42.68 µm, crystallinity degree of 61.6 %, and cellulose purity of 92.5 %. Meanwhile, similar parameters with 4 N HCl solution produced MCC with the same purity but higher crystallinity (65.6 %), higher mean size, 67.62 µm, and higher aspect ratio. SEM images showed that 4 N HCl caused less detrimental and erosive action, and less fragmentation on cellulose microfibrils compared to 30 wt % H2SO4. The study's outcome supports the feasibility of corn husks to produce cellulose and MCC for further applications. [ABSTRACT FROM AUTHOR]

High-sensitivity solutions for real-time and on-line multi-component gas detection are required in coal mine safety, petrochemical and storage and transportation industries, atmospheric and environmental monitoring, combustion diagnosis, and industrial process monitoring and control. In optical technology, Tunable Diode Laser Absorption Spectroscopy (TDLAS) has been proven to be an advanced technology for detection of multi-component gas, which benefits from the high sensitivity, good selectivity, fast response and anti-disturbance of TDLAS sensors. In detection of multi-component gas, the presence of non-negligible cross-interference, cost and performance requirements become a primary concern in the design of many detection schemes. In this review article, the application of TDLAS technology in multi-component gas detection will be discussed in two categories: (I) Multiple lasers for detection of multi-component gas without cross-interference. (II) A single laser for detection of multi-component gas. This article outlines the advantages and disadvantages of applying various schemes in the two categories when TDLAS is applied to multi-component detection, with the aiming of providing ready-made guidance for multi-component detection under various applications. [ABSTRACT FROM AUTHOR]

Commercially available 316L (1.4404) stainless steel is commonly used for industrial filtration due to its combination of good material properties, particularly its corrosion resistance, which is a critical factor for filters in corrosive (e.g., saltwater) environments. Recently, laser powder bed fusion (LPBF) has enabled new more complex and efficient filtration pieces to be manufactured from this material. However, it is critical to know how the corrosion resistance is affected by this manufacturing strategy. Here, the corrosion resistance of LPBF manufactured 316L stainless steel is compared with wrought 316L sheet. The corrosion of the samples in saltwater was assessed with asymmetric electrochemical noise, potentiodynamic polarisation curve, and electrochemical impedance spectroscopy. The samples before and after corrosion were examined with scanning electron microscopy and energy-dispersive spectroscopy. The LPBF samples had higher corrosion resistance than the sheet samples and were more noble. The corrosion resistance of the LPBF sample increased with time, while the wrought sample corrosion resistance reduced over time. The corrosion mechanism of both samples was stable with time, formed of a passive film process and a bared material process. This paper presents the first study about the temporal evolution of the LPBF 316L stainless steel corrosion mechanism. [ABSTRACT FROM AUTHOR]

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This article describes the temporal evolution of rotationally and vibrationally non-Boltzmann CN X2Σ+ formed behind reflected shock waves in N2–CH4 mixtures at conditions relevant to atmospheric entry into Titan. A novel ultrafast (i.e., femtosecond) laser absorption spectroscopy diagnostic was developed to provide broadband (≈400 cm−1) spectrally resolved (0.02 nm resolution) measurements of CN absorbance spectra belonging to its B2Σ+ ← X2Σ+ electronic system and its first four Δv = 0 vibrational bands (v″ = 0, 1, 2, 3). Measurements were acquired behind reflected shock waves in a mixture with 5.65% CH4 and 94.35% N2 at initial chemically and vibrationally frozen temperatures and pressures of 4400–5900 K and 0.55–0.75 bar, respectively. A six-temperature line-by-line absorption spectroscopy model for CN was developed to determine the rotational temperature of CN in v″ = 0, 1, 2, and 3, as well as two vibrational temperatures via least-squares fitting. The measured CN spectra revealed rotationally and vibrationally non-Boltzmann population distributions that strengthened with increasing shock speed and persisted for over 100 µs. The measured vibrational temperatures of CN initially increase in time with the increasing CN mole fraction and eventually exceed the expected post-shock rotational temperature of N2. The results suggest that strong chemical pumping is ultimately responsible for these trends and that, at the conditions studied, CN is primarily formed in high vibrational states within the A2Π or B2Σ+ state at characteristic rates, which are comparable to or exceed those of key vibrational equilibration processes. [ABSTRACT FROM AUTHOR]

Infrared (IR) spectroscopy using ultracold helium nanodroplet matrices has proven to be a powerful method to interrogate encapsulated ions, molecules, and clusters. Due to the helium droplets' high ionization potential, optical transparency, and ability to pick up dopant molecules, the droplets offer a unique modality to probe transient chemical species produced via photo- or electron impact ionization. In this work, helium droplets were doped with acetylene molecules and ionized via electron impact. Ion-molecule reactions within the droplet volume yield larger carbo-cations that were studied via IR laser spectroscopy. This work is focused on cations containing four carbon atoms. The spectra of C4H2+, C4H3+, and C4H5+ are dominated by diacetylene, vinylacetylene, and methylcyclopropene cations, respectively, which are the lowest energy isomers. On the other hand, the spectrum of C4H4+ ions hints at the presence of several co-existing isomers, the identity of which remains to be elucidated. [ABSTRACT FROM AUTHOR]

The primary and secondary fragmentation dynamics of iodobenzene following its ionization at 120 eV were determined using three-dimensional velocity map imaging and covariance analysis. Site-selective iodine 4d ionization was used to populate a range of excited polycationic parent states, which primarily broke apart at the carbon-iodine bond to produce I+ with phenyl or phenyl-like cations (C n H x + or C n H x 2 + , with n = 1 – 6 and x = 1 – 5). The molecular products were produced with varying degrees of internal excitation and dehydrogenation, leading to stable and unstable outcomes. This further allowed the secondary dynamics of C 6 H x 2 + intermediates to be distinguished using native-frame covariance analysis, which isolated these processes in their own centre-of-mass reference frames. The mass resolution of the imaging mass spectrometer used for these measurements enabled the primary and secondary reaction channels to be specified at the level of individual hydrogen atoms, demonstrating the ability of covariance analysis to comprehensively measure the competing fragmentation channels of aryl cations, including those involving intermediate steps. [ABSTRACT FROM AUTHOR]

Membranes are crucial for the functionality of membrane proteins in several cellular processes. Time-resolved infrared (IR) spectroscopy enables the investigation of interaction-induced dynamics of the protein and the lipid membrane. The photoreceptor and proton pump bacteriorhodopsin (BR) was reconstituted into liposomes, mimicking the native purple membrane. By utilization of deuterated lipid alkyl chains, corresponding vibrational modes are frequency-shifted into a spectrally silent window that allows us to monitor lipid dynamics during the photoreaction of BR. Our home-built quantum cascade laser (QCL)-based IR spectrometer covers all relevant spectral regions to detect both lipid and protein vibrational modes. QCL-probed transients at single wavenumbers are compared with the previously performed step-scan Fourier-transform IR measurements. The absorbance changes of the lipids could be resolved by QCL-measurements with a much better signal-to-noise ratio and with nanosecond time resolution. We found a correlation of the lipid dynamics with the protonation dynamics in the M intermediate. QCL spectroscopy extends the study of the protein's photocycle toward dynamics of the interacting membrane. [ABSTRACT FROM AUTHOR]

The infrared response of a system of two vibrational modes in a cavity is calculated by an effective non-Hermitian Hamiltonian derived by employing the nonequilibrium Green's function (NEGF) formalism. Degeneracies of the Hamiltonian (exceptional points, EPs) widely employed in theoretical analysis of optical cavity spectroscopies are used in an approximate treatment and compared with the full NEGF. Qualitative limitations of the EP treatment are explained by examining the approximations employed in the calculation. [ABSTRACT FROM AUTHOR]

In this study, we present the design and fabrication of a V-shaped resonator that served as an absorption chamber in a laser spectroscopy system for water stable isotope measurement (2H, 17O, 18O) based on optical feedback cavity-enhanced absorption spectroscopy. In the design of a resonator, its length and the radius of curvature of the mirrors guarantee the optical stability of the system. The resonator mirrors are designed considering the condition of stability and based on the desired mode structure of the resonator output. The V-shaped resonator is designed with two arms of 40 cm and inner diameters of 5 mm making an angle of 1.7°. This resonator has an internal volume of 20 cm3 which provides fast response of laser spectrometer. The high reflectivity of mirrors leads to an effective absorption optical path length of 13 km and a high finesse optical resonator of Ƒ~52،000. These values allow low concentration water vapor isotope analyses and resolution of the absorption spectrum of isotopes for accurate isotope measurements, respectively. Resonator mirrors are designed using Mcleod software to have maximum reflectance at a wavelength of 1.4 micrometers. By making a V-shaped optical resonator for measuring stable isotopes of water and subsequent development for measuring stable isotopes of other elements, the possibility of developing the application of stable isotopes in different areas of research will be provided.

The results of the development and research of the technological process for manufacturing spherical vapor cells are presented. Such cells are used in quantum devices, such as magnetometers, gyroscopes, and atomic clocks. Their work is based on optical pumping and detection of the state of alkali metal vapors, in particular cesium. To increase the lifetime of cesium spin polarization in the vapor cell, it is filled with a buffer inert gas. The quality of cell manufacturing directly affects such device characteristics as the width of resonance lines and the achievable signal-to-noise ratio. The proposed cell manufacturing technology simplifies the technological process, eliminates the use of specialized equipment, and increases the reproducibility of results associated with chemical reactions of an alkali metal with foreign impurities in a buffer gas. This is achieved by detecting the formed compounds and excluding them from the composition of the gaseous environment of the cells through the selection of a reasonable sequence of technological operations in the cell manufacturing cycle. The use of traditional methods of X-ray diffraction is associated with the need to depressurize the vapor cell with cesium which leads to the inevitable reaction of cesium with components of the air environment. The work proposes a two-stage analytical assessment of the composition of the gas mixture. At the first stage, the thermodynamic resolution of all possible reactions in the cesium-nitrogen-impurity oxygen system is determined. At the second stage, the color spectrum of the spectra of experimentally obtained reaction products is compared with the color of the products of thermodynamically allowed interactions. Thermodynamic analysis based on a two-stage approach made it possible to identify the formation of cesium suboxides in a vapor cell when it was heated in the temperature range of 273–700 K. To exclude them from the composition of the vapor cell, a sequence of operations was proposed. It involves the formation of an ampoule using the glass blowing method which has a technological cylindrical part and a spherical cell connected to it by a constriction. High purity cesium encapsulated in a glass shell is placed into the technological part of the ampoule, after which the ampoule is evacuated. After opening the capsule with cesium, thermal distillation of pure cesium into a spherical zone takes place. The technological process is completed by filling the cell with buffer gas, after which it is sealed off. The absence of heating during filling a vapor cell with nitrogen significantly simplifies the technological process and minimizes the amount of foreign impurities in the form of cesium suboxides in the gas mixture.

Microplastics are one of the concerning environmental pollutants because of their ubiquity. Their capability to adsorb other environmental pollutants increases the risk even further. Existing identification approaches for microplastic characterization for polymer class and their surface-adsorbed heavy metal detection require the utilization of multiple resources and expertise. The article discusses the applicability of a custom-made hyphenated Laser Induced Breakdown Spectroscopy (LIBS)—Raman spectroscopic system in characterizing microplastics by comparing the analytical performance with conventional methods such as Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy, confocal Raman spectroscopy, and Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDS). Raman analysis identified polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) plastics, which is confirmed by confocal Raman and FTIR study of the same. LIBS study of microplastics detected heavy metals such as Al, Ni, Co, and Zn, along with Ca and Mg trace elements. The cross-examination with EDS validates these trace elements' presence on the microplastics' surface. The results of the reported LIBS-Raman analysis and its validity evaluated using conventional gold-standard methods show the applicability of the proposed methodology in characterizing microplastics from environmental resources with less or no sample preparation in short time. [ABSTRACT FROM AUTHOR]

The corrosion resistance of rebars coated with four different cementitious coatings containing nanoparticles of CaCO3, Fe2O3, SiO2 and ZrO2 is reported. The corrosion resistance of nanoparticle-admixed cementitious polymer on rebars in NaCl medium is evaluated using potentiodynamic polarization (PDP) and impressed voltage test (IVT). The corrosion products of coated rebars, without mortar or concrete cover, after immersion in chloride medium were examined using x-ray diffraction (XRD), scanning electron microscopy (SEM) and laser Raman spectroscopy (LRS). The crack initiation time for rebars coated with nanoparticle-admixed cementitious coating in the absence of concrete is significantly higher than uncoated rebars. PDP and IVT results indicate the best coating is CaCO3 coating, and the coating performance followed the trend CaCO3 > SiO2 > ZrO2 > Fe2O3. The results of these studies indicate that the size as well as the distribution of nanoparticles is crucial for the effective pore filling in the cementitious coating. The superior corrosion protection performance of nanoparticle-incorporated coating is attributed to the effective pore-filling capacity and the better physical barrier formed on the rebars. These findings on nanoparticle-admixed cement coated rebars may have important applications in designing high-performance rebar coating with superior corrosion resistance for aggressive conditions. [ABSTRACT FROM AUTHOR]

Objective: Rhodopsin from the eubacterium Exiguobacterium sibiricum (ESR) performs the lightdependent proton pumping function. The operation of ESR is based on the ultrafast photochemical reaction of isomerization of the retinal chromophore, which triggers dark processes closed in a photocycle. Many parameters of the photocycle are determined by the presence of a hydrogen bond between the primary counterion Asp85 and the chromophore. ESR in detergent micelles pumps protons most efficiently at pH > 9, when such a bond is most probable. Methods: In the present study, the photochemical reaction of ESR at pH 9.5 was investigated by femtosecond laser absorption spectroscopy. Results and Discussion: It was shown that photoisomerization of the chromophore group occurs in 0.51 ps, with the contribution from the reactive excited state being ca. 80%. A comparison with the earlier obtained data for pH 7.4 showed that, at pH 9.5, the reaction proceeds much faster and more efficiently. Conclusions: The present results confirm the important role of the chromophore group counterion in the photoactivated processes of rhodopsins. [ABSTRACT FROM AUTHOR]

Lanthanides and actinides are emerging contaminants, but little is known about their uptake and distribution by plants and their interactions in the rhizosphere. To better understand the fate of these metals in plants, the bioassociation of 2, 20 and 200 µM Eu(III) by five hydroponically grown crops endemic to Europe was assessed. The metal's concentration and its speciation were monitored by inductively coupled plasma mass spectrometry and laser spectroscopy, whereas root exudation was investigated by chromatographic methods. It has been shown, that Eu(III) bioassociation is a two-stage process, involving rapid biosorption followed by accumulation in root tissue and distribution to the stem and leaves. Within 96 h of exposure time, the plant induces a change of Eu(III) speciation in the liquid medium, from a predominant Eu(III)aquo species, as calculated by thermodynamic modelling, to a species with longer luminescence lifetime. Root exudates such as citric, malic, and fumaric acid were identified in the cultivation medium and affect Eu(III) speciation in solution, as was shown by a change in the thermodynamic model. These results contribute to a comprehensive understanding of the fate of lanthanides in the biosphere and provide a basis for further investigations with the chemical analogues Cm(III) and Am(III). [ABSTRACT FROM AUTHOR]

Melanin is a crucial pigment in melanomagenesis. Its fluorescence in human tissue is exceedingly weak but can be detected through advanced laser spectroscopy techniques. The spectral profile of melanin fluorescence distinctively varies among melanocytes, nevomelanocytes, and melanoma cells, with melanoma cells exhibiting a notably "red" fluorescence spectrum. This characteristic enables the diagnosis of melanoma both in vivo and in histological samples. Neuromelanin, a brain pigment akin to melanin, shares similar fluorescence properties. Its fluorescence can also be quantified with high spectral resolution using the same laser spectroscopic methods. Documented fluorescence spectra of neuromelanin in histological samples from the substantia nigra substantiate these findings. Our research reveals that the spectral behavior of neuromelanin fluorescence mirrors that of melanin in melanomas. This indicates that the typical red fluorescence is likely influenced by the microenvironment around (neuro)melanin, rather than by direct pigment interactions. Our ongoing studies aim to further explore this distinctive "red" fluorescence. We have observed this red fluorescence spectrum in post-mortem measurements of melanin in benign nevus. The characteristic red spectrum is also evident here (unlike the benign nevus in vivo), suggesting that hypoxia may contribute to this phenomenon. Given the central role of hypoxia in both melanoma development and treatment, as well as in fundamental Parkinson's disease mechanisms, this study discusses strategies aimed at reinforcing the hypothesis that red fluorescence from (neuro)melanin serves as an indicator of hypoxia. [ABSTRACT FROM AUTHOR]

Raman spectroscopy and laser ablation‐inductively coupled plasma‐mass spectrometry were used to characterize the chemical composition of 34 red garnet beads from Lower Nubian sites, dated between about 3200 BCE and 600 CE. All beads from the A‐Group to the Meroitic period feature a similar calcium‐poor almandine composition (69%–78% almandine, 15%–22% pyrope, 2%–6% grossular, 3%–9% spessartine), which differs from other calcium‐poor almandine garnet types, sourced mostly from Indian deposits in Antiquity. The Nubian beads constitute a new garnet type, named "cluster I", featuring high yttrium (180 to 1205 ppm), moderately low chromium (13–70 ppm), and high scandium (119–213 ppm) concentrations. Their compositions match with previous and two new analyses from two alluvial garnet deposits, Wadi El‐Haraz and Wadi Abu Dom, near the Fourth Cataract of the Nile in Upper Nubia, about 670 km as the crow flies from the Lower Nubian graves. Garnet trade between the Bayuda desert and Lower Nubia sites, and possibly even Egypt, flourished for almost four millennia. Northeastern Africa is the cradle for the oldest use of a gemstone that is harder than quartz—the red almandine garnet. A Post‐Meroitic bead, the youngest in the assembly, displays an unusual faceting, a diamond tipped drill hole, excellent polish, distinct short‐ and long‐prismatic colorless mineral inclusions, and a calcium‐ and manganese‐poor pyrope composition. This suggests that it was not of a local, Nubian, production, but imported, most probably from a South Asian site. [ABSTRACT FROM AUTHOR]

Glasses that contain Erbium oxide as a dopant exhibit garnered considerable interest for its use in photonic applications, primarily because of the intra-4f sublevel transitions of Erbium ions, which enable emission in the technologically significant 1.5 μm communications window. In this work, a series of Erbium oxide doped sodium lithium borate glasses were synthesized via melt quenching with compositions x Er 2 O 3 -(55-x)B 2 O 3 –25Li 2 O–10Na 2 O–5CaO–3SrO–2Al 2 O 3 (x = 0, 1, 2, 3, and 5 mol%). An investigation was conducted to examine the consequences of Er3+ on the crystal structure and laser spectroscopy. Furthermore, the optical properties of the samples that were created. XRD analysis showed degradation of the glass network with increasing Er 2 O 3 content due to disruption of boroxol rings. FTIR spectra indicated variations in BO 3 /BO 4 ratios and Er–O vibrations with doping. Absorption spectra revealed characteristic Er3+ f-f transitions and a redshift in the UV edge. The bright field imaging proved the effect of Er3+ on the homogeneity of the surfaces. Meanwhile, 3D laser Raman mapping chemically proves the good distribution of Er 2 O 3 on the glass surface. With an excitation under 980 nm, visible emissions at 550 and 660 nm, along with NIR emission at 1550 nm arising from Er3+ 4f levels, were observed. The results demonstrate that Er3+ doping effectively modifies the glass structure and optical properties. The borate glass host provides an excellent platform for customized erbium-doped photonic devices operating in the telecom C-band. [ABSTRACT FROM AUTHOR]

Tunable diode laser spectroscopy (TDLS) is a measurement technique with high spectral resolution. It is based on tuning the emission wavelength of a semiconductor laser by altering its current and/or its temperature. However, adjusting the wavelength leads to a change in emission intensity. For applications that rely on modulated radiation, the challenge is to isolate the true spectrum from the influence of extraneous instrumental contributions, particularly residual intensity and wavelength modulation. We present a novel approach combining TDLS with interferometric techniques, exemplified by the use of a Mach–Zehnder interferometer, to enable the separation of intensity and wavelength modulation. With interferometrically enhanced intensity modulation, we reduced the residual wavelength modulation by 83%, and with interferometrically enhanced wavelength modulation, we almost completely removed the residual derivative of the signal. A reduction in residual wavelength modulation enhances the spectral resolution of intensity-modulated measurements, whereas a reduction in residual intensity modulation improves the signal-to-noise ratio and the sensitivity of wavelength-modulated measurements. [ABSTRACT FROM AUTHOR]

This study focused on the creation of Ag-MnO2 nanosheet composites by combining Ag and MnO2 nanosheets with the use of surfactant and organic solvents. The as-prepared adsorbents were analyzed for their oxidation properties in removing ethyl mercaptan through various characterization techniques including x-ray diffraction (XRD), transmission electron microscopy coupled with energy-dispersive x-ray spectroscopy, laser Raman spectroscopy, N2 adsorption–desorption isotherm analysis, and Fourier transformation infrared spectroscopy. The research findings revealed that Ag-MnO2-NS exhibits strong electromagnetic adsorption properties due to the robust interaction between silver and sulfur. The interaction between silver (Ag) and manganese dioxide (MnO2) was found to facilitate the oxidation of ethyl mercaptan (EM) into ethyl sulfonate and organosulfate. The combined effect of MnO2-NS and Ag was observed to enhance both the adsorption and catalytic oxidation of EM. This study delved into the adsorption and oxidation processes of EM using composite materials formed by combining silver nanoparticles and manganese dioxide nanosheets. The mechanism of oxidative adsorption was thoroughly analyzed through characterization, providing valuable insights for the efficient removal of EM. [ABSTRACT FROM AUTHOR]

Gas evolution is fundamentally problematic in rechargeable batteries, and may lead to swelling, smoking, and device‐level failure. In laboratories, monitoring gas evolution can help understand dynamic chemical events inside battery cells, such as the formation of solid‐electrolyte interphases, structural change of electrodes, and electrolyte degradation reactions. However, gassing in commercial batteries, discrete or continuous, is not monitored due to a lack of compatible sensing technologies. Here we describe the working principles of four real‐time gas monitoring technologies for lithium‐ion batteries. Gassing mechanisms and reaction pathways of five major gaseous species, namely H2, C2H4, CO, CO2, and O2, are comprehensively summarized. Since pertinent progress has been made on the optical fiber‐based sensing of strain, pressure, and temperature of various battery cells recently, special emphasis has been given to fiber‐based laser spectroscopy for gas detection. The technical details of the fiber‐enhanced photothermal spectroscopy are compared with the four gas sensing technologies, and the commercialization possibilities are discussed. Owing to its small size, flexibility, and robustness, fiber‐based sensing technology can be compatible with almost all kinds of battery cells, showcasing their great potential in various applications. It is envisioned that gas‐event monitoring of rechargeable cells can be unlocked soon by utilizing fiber‐based gas spectroscopy. [ABSTRACT FROM AUTHOR]

According to old theories of sweetness, the perception of sweet substances is closely linked to the arrangement of atoms within them. To assess the validity of these theories, we conducted an analysis of the structure of the artificial sweetener dulcin for the first time, utilizing microwave spectroscopy and a laser ablation source. These techniques have enabled the identification of two conformers, which are stabilized by an intramolecular hydrogen bond between the amino group and the phenyl ring. The observed conformations were examined in light of the Shallenberger‐Acree‐Kier molecular theory of sweet taste, and they align with the hypothesized criteria. Furthermore, the study illustrates how conformational relaxation can alter the equilibrium conformational distribution, resulting in the absence of certain conformers in the conformational landscape. [ABSTRACT FROM AUTHOR]

Detecting and mitigating mechanical damage in apples during picking and transportation is a critical concern in the agricultural industry. This paper investigates the optimization of a pattern recognition model using single-wavelength laser relaxation spectroscopy for the purpose of apple mechanical damage detection. We conducted experiments using Red Fuji apples as our sample dataset and designed a single-wavelength laser relaxation spectroscopy system to collect spectral data. The 1823 sets of data from 45 apples were collected. To enhance the quality of the data, we applied the Min–Max standardization algorithm for preprocessing. Subsequently, we employed multiple pattern recognition models, including Support Vector Machine (SVM), Cross-Validation Optimized Support Vector Machine (CV-SVM), Relevance Vector Machine (RVM), and Sparrow Search Algorithm Optimized Relevance Vector Machine (SSA-RVM), to establish models for apple damage detection. Our study involved a comparison of the efficiency and accuracy of these models. Our findings indicate that CV-SVM emerged as the most stable model for apple damage detection, achieving an impressive accuracy rate of 93.19%. Furthermore, to enhance the classification performance, we applied Multiple Measurement Classification Recognition (MMCR). The CV-SVM-MMCR model demonstrated superior classification abilities, with a detection accuracy rate of 97.5%. Notably, our proposed method offers several advantages, including ease of operation, rapid analysis, and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Carbene‐metal‐amides (CMAs) are emerging delayed fluorescence materials for organic light‐emitting diode (OLED) applications. CMAs possess fast, efficient emission owing to rapid forward and reverse intersystem crossing (ISC) rates. The resulting dynamic equilibrium between singlet and triplet spin manifolds distinguishes CMAs from most purely organic thermally activated delayed fluorescence emitters. However, direct experimental triplet characterization in CMAs is underutilized, limiting our detailed understanding of the ISC mechanism. In this work, we combine time‐resolved spectroscopy with tuning of state energies through environmental polarity and metal substitution, focusing on the interplay between charge‐transfer (3CT) and local exciton (3LE) triplets. Unlike previous photophysical work, we investigate evaporated host : guest films of CMAs and small‐molecule hosts for increased device relevance. Transient absorption reveals an evolution in the triplet excited‐state absorption (ESA) consistent with a change in orbital character between hosts with differing dielectric constants. Using quantum chemical calculations, we simulate ESAs of the lowest triplet states, highlighting the contribution of only 3CT and donor‐moiety 3LE states to spectral features, with no strong evidence for a low‐lying acceptor‐centered 3LE. Thus, our work provides a blueprint for understanding the role of triplet excited states in CMAs which will enable further intelligent optimization of this promising class of materials. [ABSTRACT FROM AUTHOR]

Here, the optical properties of the Nafion polymer membrane containing colloidal CdSe/CdS/ZnS nanocrystals embedded by diffusion have been studied. The CdSe/CdS/ZnS nanocrystals have a core/shell/shell appearance. All experiments were carried out at room temperature (22 ± 2) °C. A toluene solution was used to provide mobility to the active sulfone groups of the Nafion membrane and to embed the nanocrystals inside the membrane. The diffusion process of colloidal CdSe/CdS/ZnS nanocrystals into Nafion proton exchange membrane has resulted in a new molecular complex "Nafion–colloidal CdSe/CdS/ZnS nanocrystals". The kinetics of the nanocrystals embedding into the membrane matrix was investigated using luminescence analysis and absorption spectroscopy techniques. The embedding rate of CdSe/CdS/ZnS nanocrystals into the Nafion polymer membrane was approximately 4·10−3 min−1. The presence of new luminescence centers in the membrane was proved independently by laser emission spectroscopy. The luminescence spectrum of the resulting molecular complex contains intensity maxima at wavelengths of 538, 588, 643 and 700 nm. The additional luminescence maximum observed at the 643 nm wavelength was not recorded in the original membrane, solvent or in the spectrum of the semiconductor nanoparticles. The luminescence maximum of the colloidal CdSe/CdS/ZnS nanocrystals was registered at a wavelength of 634 nm. The intensity of the luminescence spectrum of the membrane with embedded nanocrystals was found to be higher than the intensity of the secondary emission peak of the initial nanocrystals, which is important for the practical use of the "Nafion–colloidal nanocrystals" complex in optical systems. The lines contained in the luminescence spectrum of the membrane, which has been in solution with colloidal nanocrystals for a long time, registered upon its drying, show the kinetics of the formation of the molecular complex "Nafion membrane–nanocrystals". Colloidal nanocrystals located in the Nafion matrix represent an analog of a luminescent transducer. [ABSTRACT FROM AUTHOR]

Tunable laser spectroscopy (TLS) with infrared (IR) imaging is a powerful tool for gas leak detection. This study focuses on direct absorption spectroscopy (DAS) that utilizes wavelength modulation to extract gas information. A tunable interband cascade laser (ICL) with an optical power of 5 mW is periodically modulated by a sawtooth injection current at 10 Hz across the methane absorption around 3271 nm. A fast and sensitive thermal imaging camera for the mid-infrared range between 3 and 5.7 µm is operated at a frame rate of 470 Hz. Offline processing of image stacks is performed using different algorithms (DAS-F, DAS-f and DAS-2f) based on the Lambert–Beer law and the HITRAN database. These algorithms analyze various features of gas absorption, such as area (F), peak (f) and second derivative (2f) of the absorbance. The methane concentration in ppm*m is determined on a pixel-by-pixel analysis without calibration. Leak localization for methane leak rates as low as 0.25 mL/min is accurately displayed in a single concentration image with pixelwise sensitivities of approximately 1 ppm*m in a laboratory environment. Concentration image sequences represent the spatiotemporal dynamics of a gas plume with high contrast. The DAS-2f concept demonstrates promising characteristics, including accuracy, precision, 1/f noise rejection, simplicity and computational efficiency, expanding the applications of DAS. [ABSTRACT FROM AUTHOR]

We report the development of a ring Yb:KGW laser oscillator with an average power of 4.22 W, a pulse duration of 312 fs at a repetition rate of 216 MHz. The ring laser oscillator is purely Kerr lens mode-locked (KLM) taking advantage of the high nonlinear refractive index of the laser crystal in spite of being pumped by a multimode laser diode. To the best of our knowledge, this is the highest average power obtained from a KLM ring Yb:KGW laser oscillator. Monitoring the repetition rate fluctuations after initial warm-up of the laser cavity, a peak to valley of only 354.28 Hz during 30 min of free-running operation has been achieved. This could make a free-running ring cavity a suitable light source for application to laser spectroscopy. Using the ring laser oscillator, we have measured the absorption of the second overtone of the ν 1 mode of NH 3 . We have also measured absorption spectra of the Yb:KGW crystal to evaluate the quality of the crystal affected by the doped impurities. [ABSTRACT FROM AUTHOR]

The Shimensi super-large tungsten polymetallic deposit is located in the Late Jurassic–Early Cretaceous Porphyry–Skarn tungsten ore belt in the south Yangtze metallogenic belt. There are three types of mineralization: veinlet-disseminated type, thick quartz vein type and hydrothermal cryptoexplosive breccia type. Based on geological studies, this paper presents new petrographic, microthermometric, laser Raman spectroscopic and hydrogen and oxygen isotope research on the fluid inclusions from the deposit. The results show that there are five different types of fluid inclusions: liquid-rich inclusions, vapor-rich inclusions, pure liquid inclusions, pure vapor inclusions, and fluid inclusions containing a solid crystal. The homogenization temperatures of the fluid inclusion range from 140 °C to 270 °C, the salinities are 3 wt.%–5 wt.% NaCleq and the densities of ore-forming fluid range from 0.64 g/cm3 to 0.99 g/cm3. For the analyses of laser Raman spectroscopy, the ore-forming fluids can be approximated by a Ca2+-Na+-SO42−-Cl− fluid system with small amounts of CO2, CH4 and N2. Otherwise, the data of the pressure, pH and Eh show a fluid metallogenic environment of low pressure, weak acid and weak reduction. The values of the homogenization temperature in the three types of orebodies suggest that the mineralization is characterized by a decrease in temperature under the conditions of fluid immiscibility. The H-O isotope values are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water, and meteoric water is added with the process of magma rising. [ABSTRACT FROM AUTHOR]

Tunable Diode Laser Absorption Spectroscopy (TDLAS) measurements of nitric oxide (NO) using a Quantum Cascade Laser (QCL) in the vicinity of 5.26 μm were conducted in a hypervelocity flow generated in the Texas A&M Hypervelocity Expansion Tunnel (HXT). The nascent NO was produced downstream of symmetric Mach reflections generated in Mach 8.5 flows with stagnation enthalpies from 6.9 to 11.1 MJ/kg. Path-averaged flow parameters of rotational and vibrational temperatures and NO concentration at a measurement rate of 30 kHz were obtained. By probing the R-branch of the fundamental absorption band in NO, thermal nonequilibrium and NO concentration levels in the post-shock region were measured. Measurements are compared to equilibrium calculations. NO equilibrium values during the 1 ms test period differ from the experimental rotational and vibrational measurements across the same time period. The experimental measurements of the rotational temperature show a consistent value around 3000 K larger than the recovered vibrational temperature across any run. The NO concentrations in all runs are near to the reported equilibrium value; often beginning higher than, and over time decaying to, the equilibrium concentration value of the specific tunnel run. [ABSTRACT FROM AUTHOR]