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A detection sensor for mid-infrared ammonia (NH3) has been developed according to wavelength modulation spectroscopy-tunable diode laser absorption spectroscopy (WMS-TDLAS) technology, which can be applied in the chemical and aquaculture industries. A 9.06 µm quantum cascade laser (QCL) and a 41.5 m multipass gas cell (MPGC) were used to increase the detection limit of NH3. Spectral optimization and the NGO-LSTM (northern goshawk optimization-long short-term memory) model applied to gas detection are designed to improve the accuracy of sensor. Among them, the design of the temperature compensation and spectral drift correction reduces the effect of temperature and other environmental factors. The original second harmonic signal was denoised using the CEEMDAN-WPD (complete ensemble empirical mode decomposition with adaptive noise-wavelet packet decomposition) algorithm. And the NGO-LSTM algorithm was applied to NH3 concentration inversion, adaptively optimizing the weight parameters. The experiment reflects that the measured value of the sensor has an excellent linear relationship with the set value (R2 0.9992). The long-term stability of the sensor was verified based on 400 ppb NH3, with an RMSE (root mean square error) of 4.754 ppb. Allan-Werle bias analysis shows that the detection limit (LoD) is approximately 792 ppt at an integration time of 232 s. Subsequent response time and atmospheric environment simulation experiments have proven that this sensor provides an efficient approach for real-time monitoring of NH3. [ABSTRACT FROM AUTHOR]

Water, as the primary volatile component in magmatic systems, has a significant impact on the formation and evolution of magma. The Tiaojishan Formation igneous rocks in the Liujiang Basin are significant products of Yanshanian volcanic activity. Although previous studies have extensively explored their geochemical characteristics, the water content of the magma in the Liujiang Basin during Yanshanian volcanic activity remains unclear. Melt inclusions, which capture the original magmatic information, serve as the most direct samples for determining the water content of magma. Based on geochemical analysis, this study quantitatively determines the water content in melt inclusions using laser Raman spectroscopy with standard samples. The results show that the lower tuff samples of the Tiaojishan Formation are characterized by high Si and Al contents, enrichment in LILEs, depletion in HFSEs, enrichment in LREEs, and depletion in HREEs. The water content in melt inclusions reveals a range of 0.99% to 4.98%, with an average of 2.62%. These characteristics jointly indicate the water-enriched acidic magmatic activity during the early Tiaojishan period in this area. Combining the water content of melt inclusions with the large-scale volcanic eruptions in the stage, this study suggests that high water content in the magma enhanced the eruptive dynamics of the magmatic system, making it a contributing factor to the large-scale volcanic eruption. [ABSTRACT FROM AUTHOR]

Multimodal imaging (MMI) has emerged as a powerful tool in clinical research, combining different imaging modes to acquire comprehensive information and enabling scientists and surgeons to study tissue identification, localization, metabolic activity, and molecular discovery, thus aiding in disease progression analysis. While multimodal instruments are gaining popularity, challenges such as non-standardized characteristics, custom software, inadequate commercial support, and integration issues with other instruments need to be addressed. The field of multimodal imaging or multiplexed imaging allows for simultaneous signal reproduction from multiple imaging strategies. Intraoperatively, MMI can be integrated into frameless stereotactic surgery. Recent developments in medical imaging modalities such as magnetic resonance imaging (MRI), and Positron Emission Topography (PET) have brought new perspectives to multimodal imaging, enabling early cancer detection, molecular tracking, and real-time progression monitoring. Despite the evidence supporting the role of MMI in surgical decision-making, there is a need for comprehensive studies to validate and perform integration at the intersection of multiple imaging technologies. They were integrating mass spectrometry-based technologies (e.g., imaging mass spectrometry (IMS), imaging mass cytometry (IMC), and Ion mobility mass spectrometry ((IM-IM) with medical imaging modalities, offering promising avenues for molecular discovery and clinical applications. This review emphasizes the potential of multi-omics approaches in tissue mapping using MMI integrated into desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI), allowing for sequential analyses of the same section. By addressing existing knowledge gaps, this review encourages future research endeavors toward multi-omics approaches, providing a roadmap for future research and enhancing the value of MMI in molecular pathology for diagnosis. [ABSTRACT FROM AUTHOR]

Directly converting methane to methanol with solar light and eco‐friendly oxidants is challenging due to single‐step conversion process where the designed active sites commonly cleave C─H bonds in both methane and methanol. Herein, a novel method is proposed to break activity‐selectivity trade‐off in methane conversion to methanol through interface engineering. Taking BiOI/BN as a proof‐of‐concept model, it's discovered that engineered interface provides distinct active sites for methane activation and overoxidation products photoreduction. Based on in situ infrared spectroscopy, ultrafast laser spectroscopy, and theoretical calculations, it is unlocked that the engineered interface induces the passivation of original trap states in BiOI component, greatly hindering ultrafast trap‐mediated recombination of photo‐induced carriers (≈39.7 ps). Benefiting from it, long‐lived electrons could directly participate in active radicals generation, ensuring effective methane activation. Subsequently, overoxidation carbon intermediates and protons are captured by active sites from the BN component and rapidly accumulated on the surface. This enables effective injection of electrons into bonding orbitals of C─H bonds in methanol, accelerating the occurrence of C─H re‐bonding process. Ultrafast photo‐induced charge and carbon intermediates transfer at interfaces results in high methane conversion rate of 15.5% under atmospheric pressure and maintains methanol selectivity of 86.4% for 24 h long‐time reaction process. [ABSTRACT FROM AUTHOR]

Laser spectroscopy of atomic hydrogen and hydrogen-like atoms is a powerful tool for tests of fundamental physics. The 1S–2S transition of hydrogen in particular is a cornerstone for stringent Quantum Electrodynamics (QED) tests and for an accurate determination of the Rydberg constant. We report laser excitation of the 1S–2S transition in singly-ionized helium (3He+), a hydrogen-like ion with much higher sensitivity to QED than hydrogen itself. The transition requires two-photon excitation in the challenging extreme ultraviolet wavelength range, which we achieve with a tabletop coherent laser system suitable for precision spectroscopy. The transition is excited by combining an ultrafast amplified pulse at 790 nm (derived from a frequency comb laser) with its 25th harmonic at 32 nm (produced by high-harmonic generation). The results are well described by our simulations and we achieve a sizable 2S excitation fraction of 10−4 per pulse, paving the way for future precision studies. A measurement of the 1S-2S transition frequency in He+ would enable fundamental physics tests, but the required extreme ultraviolet radiation makes this a challenge. The authors observe such transition using radiation produced by high-harmonic generation of frequency comb pulses, in a manner that is compatible with future precision spectroscopy. [ABSTRACT FROM AUTHOR]

We have developed a compact sensor utilizing a tunable diode laser near 1850.5 nm to measure H₂O absorption for wide-range temperature diagnostics. The sensor's performance was experimentally evaluated in a tube furnace at temperatures ranging from 600 to 1800 K and pressures from 3.5 to 103 kPa, showing a relative error between the measured and set temperatures of −2%–3.5%. The numerical simulations confirmed the sensor's suitability for temperature measurements between 500 and 2500 K, with the accuracy of absorbance extraction being a critical factor. The above results suggest that the sensor is highly effective for temperature measurement across a broad range and holds potential for applications in aerospace and industrial combustion diagnostics. [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]

AbstractTemperature is an important indicator for assessing the state of combustion. With the development of technology, the application of noncontact temperature measurement techniques is becoming increasingly widespread. The tunable diode laser absorption spectroscopy (TDLAS) technique is noninvasive, highly sensitive, and capable of continuous measurement. However, the TDLAS technology has limitations in terms of spatial resolution, and existing studies are homogeneous in terms of the selection of characteristic spectral lines. In this paper, two absorption lines of oxygen (O2) were innovatively selected. A 64-element array sensor was used to acquire signals. A standard high-temperature tube furnace was used to calibrate the sensor, and the mathematical relationship between the integral absorbance of the absorption lines and temperature was obtained. Finally, the accuracy and stability of the calibration results were verified. This study is important for the further investigation of temperature distribution in high-resolution combustion fields. [ABSTRACT FROM AUTHOR]

In this study, we present the synthesis and analysis of a novel, air‐stable, and solvent‐resistant phosphaalkene switch. Using this symmetric switch, we have demonstrated degenerate photoisomerization experimentally for the first time. With a combination of photochemical‐exchange NMR spectroscopy, ultrafast transient absorption spectroscopy, and quantum chemical calculations, we elucidate the isomerization mechanism of this symmetric phosphaalkene, comparing it to two other known molecules belonging to this class. Our findings highlight the critical role of the isolobal analogy between C=P and C=C bonds in governing nanoscale molecular motion and break new ground for our understanding of light‐induced molecular processes in symmetric heteroalkene systems. [ABSTRACT FROM AUTHOR]

AbstractArgon (Ar) atomic gaseous normal glow discharge is generated using two electrodes in low pressure in vacuum condition. The rate of change is constant a steady state in normal glow discharge. The shock wave is generated using the resonant absorption or induced emission in plasma state. The change of impedance is measured in terms of current or voltage of normal glow discharge. The aim of the work is to measure temporal profile voltage signal with the ionization probability and life time of two state lower and upper excited state in the plasma, theoretically calculated and experimentally. Results have been studied using Nd-YAG laser pumped tunable dye laser at pulsed width 7 ns and repetition rate 10 Hz. The opto-galvanic effect (OGE) is observed in normal glow discharge using the induced absorption and emission in one and two photon transitions. The change of impedance of normal glow discharge have been studied in temporal profile experimentally and calculated theoretically. [ABSTRACT FROM AUTHOR]

Fermentation engineering is critical for mass-producing chemicals, food additives, and medicines, where optimal culture conditions maximize microbial growth and metabolite production. Although monitoring bacterial growth during fermentation is critical, there is a lack of a non-invasive and sensitive method to directly monitor the bacterial metabolism. In this paper, a novel optical monitoring method is proposed based on tunable diode laser absorption spectroscopy. First, the detecting system consisting of a laser, detection, a homemade board, and an incubator is established and verified to be able to monitor the metabolite production of CO2 in Escherichia coli through a 25-h detection period. Second, the quantitative growth rate analysis method is specified by calculating the threshold time (TT) intervals between consecutive dilution gradients, and the threshold with the least sum of residuals is chosen as the optimal threshold. Finally, alongside varied pH and temperature settings in a simulated fermenter, we elucidated the influence of these factors on E. coli metabolism curves and calculated the growth rates via TT, identifying 38°C as the optimal temperature and 7.0 as the optimal pH. This study presents a novel approach to reveal optimal culture conditions during fermentation holding promises for online real-time monitoring in the future. [ABSTRACT FROM AUTHOR]

A new gas analytical technique for infrared laser spectroscopy combined with differential pressure measurement (IR-DP) is developed. The basic idea of this technique is that the absorption process of molecules by laser irradiation is monitored as the pressure enhancement in a gas cell by use of a differential pressure gauge. The system is composed of a tunable IR laser system, sample cell, differential pressure gauge, and data accumulation system. Using this system, the measurements of the IR absorption spectra for cyclohexane (50 ppm) and ammonia (100 ppm) are demonstrated. By comparison of the current IR-DP spectra with conventional Fourier-transform infrared spectra, the spectral resolution is found to be about 3 cm−1, reflecting the laser resolution. Furthermore, the estimated pressure enhancement based on a simple model is consistent with the experimental results. These results suggest that the newly developed IR-DP technique is one of a powerful tool for trace gas detection. [ABSTRACT FROM AUTHOR]

An instrument for the simultaneous characterization of thin films by Raman spectroscopy and electronic transport down to 3.7 K has been designed and built. This setup allows for the in situ preparation of air-sensitive samples, their spectroscopic characterization by Raman spectroscopy with different laser lines and five-probe electronic transport measurements using sample plates with prefabricated contacts. The lowest temperatures that can be achieved on the sample are directly proven by measuring the superconducting transition of a niobium film. The temperature-dependent Raman shift and narrowing of the silicon F2g Raman line are shown. This experimental system is specially designed for in situ functionalization and optical spectroscopic and electron transport investigation of thin films. It allows for easy on-the-fly change of samples without the need to warm up the cryomanipulator. [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]

Laser spectroscopy offers a significant tool for revealing specific molecular details with the desired accuracy and sensitivity. However, it poses challenges to maintain high sensitivity when targeting a micro‐region. Here, a dual‐enhanced photothermal approach is presented using a high‐finesse fiber Fabry–Pérot (F–P) cavity, tailored for highly sensitive chemical sensing with nanoliter‐scale light–matter interaction. A spheric surface (diameter: 50 µm, radius of curvature: 910 µm) is created on the fiber tip using focused ion beam milling. By adding a high‐reflectivity dielectric coating to the spheric surface, a fiber F–P cavity is obtained with a length of 473 µm and a finesse exceeding 4000. The intra‐cavity pump light within the gas‐filled fiber cavity generates a strong photothermal effect upon gas absorption. This effect induces phase modulation, which is amplified and detected by coupling a probe laser to the fiber cavity‐based interferometer. A minimum detection limit of 10 parts‐per‐billion (ppb) of C2H2 at 1530.37 nm is demonstrated using only 1 mW of pump power, corresponding to a normalized noise equivalent absorption coefficient of 9.1×10−11 cm−1∙W∙Hz−1/2. This platform breaks the bottleneck of ultrasensitive gas detection with a very short light–matter interaction length, promising significant advancements in microscale chemical analysis through optical investigations. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots of CsPbBr3 perovskites have been synthesized. The average size and polydispersity of nanocrystals were determined to be 8.3 nm and 16%, respectively. Thin films were made based on the obtained nanocrystals using drop-casting and spin-coating methods. The charge carrier transport process was studied using the technique of femtosecond laser pump–probe spectroscopy. An interpretation of the shift in the bleaching peak as a function of time is proposed. The mobility of charge carriers in films has been estimated using the Einstein–Smoluchowski equation. [ABSTRACT FROM AUTHOR]

The monitoring of acetone in exhaled breath is expected to provide a noninvasive and painless method for dynamic monitoring of summarized physiological metabolic status during obesity treatment. Although the commonly used Mass Spectrometry (MS) technology has high accuracy, the long detection time and large equipment size limit the application of daily bedside detection. As for the real-time and accurate detection of acetone, the gas sensor has become the best choice of gas detection technology, but it is easy to be disturbed by water vapor in breath gas. An integrated breath gas detection system based on cavity ring-down spectroscopy (CRDS) is reported in this paper, which is a laser absorption spectroscopy technique with high-sensitivity detection and absolute quantitative analysis. The system uses a 266 nm single-wavelength ultraviolet laser combined with a breath gas pretreatment unit to effectively remove the influence of water vapor. The ring-down time of this system was 1.068 μs, the detection sensitivity was 1 ppb, and the stability of the system was 0.13%. The detection principle of the integrated breath gas detection system follows Lambert–Beer's law, which is an absolute measurement with very high detection accuracy, and was further validated by Gas Chromatography–Mass Spectrometer (GC-MS) testing. Significant differences in the response of the integrated breath gas detection system to simulated gases containing different concentrations of acetone indicate the potential of the system for the detection of trace amounts of acetone. Meanwhile, the monitoring of acetone during obesity treatment also signifies the feasibility of this system in the dynamic monitoring of physiological indicators, which is not only important for the optimization of the obesity treatment process but also promises to shed further light on the interaction between obesity treatment and physiological metabolism in medicine. [ABSTRACT FROM AUTHOR]

A review is given of precision measurements of hyperfine constants and nuclear g-factors measured with ions confined in ion traps. The nuclear physics observables which can be extracted from these types of measurements are discussed. The feasibility of future nuclear structure studies using precision atomic spectroscopy of trapped radioactive atoms, produced with accelerator-driven approaches, is discussed. [ABSTRACT FROM AUTHOR]

Drinking water contamination by microplastic particles is a global concern that is becoming increasingly common due to consumer abuse, and we use laser fractionation spectroscopy to examine what microplastic particles in water packaging can do. Several types of bottled water were sampled at several manufacturing facilities in Baghdad. The presence of the measured micropolymer species in water was immediately classified and detected using a laser production resolution spectrometer as well as signal and plasma scattering spectra, various MP polymers "polyethylene terephthalate, polystyrene, polypropylene, polyethylene, and polyvinyl chloride" are five polymers that were successfully detected in drinking water to validate the ability to identify health risk factors based on potential environmental risk index (RI) and potential environmental risk factors (Tin), the results are calculated to show that risk predicates have evolved over a decade depending on the risk factors. To do. The smallest particle was 20 microns and the largest particle was 63.4 microns. Microplastics were detected in 5 out of 10 samples, PET in 4 samples, PS and PP in 2 samples, and PVC in sample 1, the most common polymer in bottled water is polyethylene. The average C/H ratios of the five samples were PE (1.76), PET (1.21), PS (1.52), PP (1.23), and PVC (0.99), on average, the measured trends of C/H values were [PE greater than PS], [PP greater than PET], and [PVC greater than PET]. According to our results, the integration of LIBS technology provides a fast and efficient way to detect microplastics. It has a high resolution of fine particles, allowing the detection of very small particles associated with various adverse effects on human health. The feasibility study for water bottling was approved, and the WHO water quality criteria were confirmed. As a result, we will undertake a thorough analysis of the best water bottling quality. In this study, the initial LIBS signals of several samples were used to completely detect microplastics. Microplastics in bottled water samples have been detected and quantified using LIBS spectroscopy techniques with Ecological Potential Ecological Risk. Analytical technology is used to investigate sources, perform research, and collect relevant data, worldwide reports, and permitted statistics to deliver crucial insights and recommendations. Water samples were obtained from several locations throughout Baghdad. At the source, 2 liters of water were obtained in plastic bottles for each sample, for a total of 10 samples. Each sample is owned by the factories that supplied it. [ABSTRACT FROM AUTHOR]

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]

The crystalline morphology and glaze color of Jian Kiln oil-spot glaze porcelain exhibit artistic beauty, making it one of the typical representatives of iron-based crystallized black porcelain from the Song Dynasty in China. This study sampled a series of specimens from key temperature points during simulation experiments, employing rapid air quenching to preserve the high-temperature state, capturing the formation process of oil-spot glaze crystals in Jian kiln ceramics. Key samples were subjected to microscopic structure and phase analysis using scanning electron microscopy (SEM), laser Raman spectroscopy (LRS), and X-ray photoelectron spectroscopy (XPS), revealing the formation mechanism of oil-spot glaze crystals in Jian kiln ceramics. The results indicate that the bubbles generated from the decomposition of iron oxide at high temperatures facilitate the migration and enrichment of iron-rich particles towards the glaze surface, laying a crucial material foundation for the subsequent crystallization process. The high-temperature reducing atmosphere accelerates the decomposition reaction of iron oxide, altering the concentration of Fe2+ in the glaze, the viscosity of the melt, and the surface tension, all of which are critical conditions that promote the formation of oil-spot glaze crystals. During the cooling phase, Fe3O4 nanocrystals oxidize into ε-Fe2O3 crystals, with external iron sources migrating inward to support ε-Fe2O3 crystal growth. This process gradually leads to the formation of micrometer-scale, leaf-shaped ε-Fe2O3 crystals that fully occupy the crystalline spots. The coloration of crystalline spots is closely tied to the size of the crystals. Thus, by adjusting the cooling regime, it is possible to create iron-based crystallization glazes with innovative color effects. Furthermore, this study offers significant insights for understanding the crystallization mechanisms of other ancient Chinese high-temperature iron-based crystallization glazes. [ABSTRACT FROM AUTHOR]

The focus of the current work is the study of the effect of the photo-catalytic activity of ZnO nanoparticles. The photocatalytic destruction of methylene blue dye, a common water contaminant, was used to assess the photocatalytic efficiency of the ZnO nanoparticles from its aqueous solution by using ZnO nanoparticles thin film under UV light and laser irradiation. Sol–gel methods prepared ZnO nanoparticle thin films. X-ray diffraction and a field-emitted scanning electron microscope were utilized to examine the structure of the produced ZnO nanoparticles. An extended characterization by laser-based fluorescence and UV–visible spectroscopic techniques. The effects of operational parameters such as photo-catalyst load and contact time on photocatalytic degradation of methylene blue were investigated. The recent study's findings showed that irradiation with a UV laser increases with power density 25 µW/cm2, the photo-catalytic rate. The UV spectra show decay for the band at 664nm decreased and the concentration of M.B. in monomer form decayed to 26% of the original concentration in 24 h, while the band at 612 which is related to the dimer M.B. molecules was not affected. The laser irradiation did the same for monomer M.B. molecules in only 3 h, while the dimer decreased to 28% of its original concentration. The reaction mechanism has been discussed by molecular modelling. Quantum mechanical calculations at B3LYP/6-311g(d,p) level indicated that methylene blue changed from dimers to monomers in the existence of ZnO. The current results present a method for degrading M.B. not only in wastewater but also in the industrial waste scale. [ABSTRACT FROM AUTHOR]

We generate an atomic beam of titanium (Ti) using a "Ti-ball" Ti-sublimation pump, which is a common getter pump used in ultrahigh vacuum systems. We show that the sublimated atomic beam can be optically pumped into the metastable 3d3(4F)4s a5F5 state, which is the lower energy level in a cycling optical transition that can be used for laser cooling. We measure the atomic density and transverse and longitudinal velocity distributions of the beam through laser fluorescence spectroscopy. We find a metastable atomic flux density of 4.3(2) × 109 s−1 cm−2 with a mean forward velocity of 773(8) m/s at 2.55 cm directly downstream of the center of the Ti-ball. Owing to the details of optical pumping, the beam is highly collimated along the transverse axis parallel to the optical pumping beam and the flux density falls off as 1/r. We discuss how this source can be used to load atoms into a magneto-optical trap. [ABSTRACT FROM AUTHOR]

The decomposition components inside SF6 electrical equipment can be detected by tunable absorption spectroscopy technique, in which the concentration of CO2 reflects the insulation defect situation inside the equipment. Therefore, potential insulation faults of the equipment can be found in time by measuring the CO2 concentration accurately. To overcome the problem of poor stability of traditional least squares concentration inversion model, ISFO-KELM gas concentration inversion model based on ISFO (Improved Sailed Fish Optimizer) and KELM (Kernel Based Extreme Learning Machine) is established in this study. The optimization ability and the ability to jump out of local optimal solution of ISFO are improved by using multi - strategy initialization method, Levy random step length, Cauchy mutation and adaptive t -distribution mutation techniques. The experimental results show that this model has high accuracy and robustness, and is superior to traditional methods such as least squares method, extreme learning machine, BP (Back Propagation) neural network in stability and generalization ability, which has important significance for evaluating the operation state of SF6 electrical equipment [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]

In this work, it is aimed to study the interplay of different longitudinal mode combs corresponding to higher‐order lateral modes of broad‐area Fabry–Pérot‐type laser diodes. Coherent coupling of longitudinal modes of different mode combs influences the near‐ and far‐field pattern of the diode. Herein, commercial state‐of‐the‐art high‐power laser diodes based on the (Al,In)GaN material system in the blue spectral range with a 40 μm broad ridge are investigated. To spectrally resolve the different lateral modes, a sequential combination of a high‐resolution double grating spectrometer and a Fabry–Pérot interferometer (FPI) is used. The grating spectrometer acts as bandpass with a spectral width smaller than the free spectral range (FSR) of the FPI. The FPI with a finesse of approximately F=60$ℱ = 60$ boosts the resolution to 0.08 pm. A spectral clustering of lateral modes with increasing current and also a variation of the number of distinguishable lateral modes between 7 and 11 are observed. Within the current range from 1.25Ith to 2.25Ith, there is no clear evidence for coherent coupling. It is concluded that mode‐pulling is not strong enough to coherently couple modes on the investigated time and wavelength range. [ABSTRACT FROM AUTHOR]

In the field of questioned document examination, determining the sequence of intersecting lines is still a technical challenge. This study aims to validate whether confocal Raman spectroscopy can determine the sequence of intersecting lines created by laser prints toner and seal ink through empirical research. The study collected 110 varieties of seal ink and 1074 test pages from 66 models of laser printers available in the Chinese market. Based on the Raman spectral characteristics of the seal ink and the microscopic morphology of the toner, 13 types of seal ink and three types of laser printers were selected for further analysis, producing 78 representative samples of intersecting lines. Confocal Raman spectroscopy was applied to the examination of these samples using a point‐scanning mode for enhanced accuracy and efficiency. The experimental results demonstrate that confocal Raman spectroscopy can non‐destructively and quickly examine the sequence of intersecting lines produced by laser printer toner and seal ink. Variations in toner forms result in differing levels of difficulty in resolving intersection problems, with the sequence of intersecting lines from toner‐dense laser printers being the easiest to ascertain. In contrast, those from printers with porous and dispersed toner present a more significant challenge in examination. This study can be corroborated with other methods proposed, and more significantly, it lays the groundwork for addressing intersection problems related to other printing or writing instruments. [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]

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Abstract The focus of the current work is the study of the effect of the photo-catalytic activity of ZnO nanoparticles. The photocatalytic destruction of methylene blue dye, a common water contaminant, was used to assess the photocatalytic efficiency of the ZnO nanoparticles from its aqueous solution by using ZnO nanoparticles thin film under UV light and laser irradiation. Sol–gel methods prepared ZnO nanoparticle thin films. X-ray diffraction and a field-emitted scanning electron microscope were utilized to examine the structure of the produced ZnO nanoparticles. An extended characterization by laser-based fluorescence and UV–visible spectroscopic techniques. The effects of operational parameters such as photo-catalyst load and contact time on photocatalytic degradation of methylene blue were investigated. The recent study’s findings showed that irradiation with a UV laser increases with power density 25 µW/cm2, the photo-catalytic rate. The UV spectra show decay for the band at 664nm decreased and the concentration of M.B. in monomer form decayed to 26% of the original concentration in 24 h, while the band at 612 which is related to the dimer M.B. molecules was not affected. The laser irradiation did the same for monomer M.B. molecules in only 3 h, while the dimer decreased to 28% of its original concentration. The reaction mechanism has been discussed by molecular modelling. Quantum mechanical calculations at B3LYP/6-311g(d,p) level indicated that methylene blue changed from dimers to monomers in the existence of ZnO. The current results present a method for degrading M.B. not only in wastewater but also in the industrial waste scale.

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]

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]

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]

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 590 MeV ring cyclotron facility of the Paul Scherrer Institute are reviewed. The former experiment determined the antiproton-to-electron mass ratio as M p ¯ / m e = 1 8 3 6. 1 5 2 6 7 3 4 (1 5). In the latter, a resonant transition (n , ℓ) = (1 7 , 1 6) → (1 7 , 1 5) of pionic helium at a frequency of ν ≈ 1 8 3 7 6 0 GHz was detected. Some future perspectives are briefly described. [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]

The current gold-standard methods for cannabinoid measurement are highly sensitive, yet expensive, sophisticated, and time-consuming. This study investigated the potential of laser Raman spectroscopy as a rapid and straightforward method for the quantitative detection of three major cannabinoids: Cannabidiol (CBD), Cannabinol (CBN), and Delta-9-tetrahydrocannabinol (THC). A series of solutions of the cannabinoids extracted from Cannabis sativa were prepared in Tetrahydrofuran (THF) and measured with a Near-Infrared (NIR)-excited Raman microspectrometer. The Raman spectra were subjected to chemometrics-based multivariate analysis, employing an ordinary least square fitting method. A strong linear relationship (R² > 0.98) was observed between the Raman intensity and the concentration of all studied cannabinoids. A Raman-based prediction model of each cannabinoid was developed based on a leave-one-out cross-validation analysis, which yielded a minimum detectable concentration in the range of 0.23-0.42 mg/ml, as determined by the Root Mean Square Error of Cross Validation (RMSECV). Additionally, characteristic Raman marker bands for each cannabinoid were identified. Overall, this study presented a simple yet effective Raman spectroscopy-based technique for rapid label-free cannabinoid detection and measurement. [ABSTRACT FROM AUTHOR]

In this article, we will examine ultrafast spectroscopy techniques and applications, covering time-resolved infrared (TR-IR) spectroscopy, time resolved visible (TA) spectroscopy, two-dimensional infrared (2D-IR) spectroscopy, Kerr-gated Raman spectroscopy, time-resolved Raman and surface sum-frequency generation (SSFG) spectroscopy. In addition to introducing each technique, we will cover some basics, such as what kinds of lasers are used and discuss how these techniques are applied to study a diversity of chemical problems such as photocatalysis, photochemistry, electrocatalysis, battery electrode characterisation, zeolite characterisation and protein structural dynamics. [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]