Formaldehyde (HCHO) is a significant air pollutant in urban environments, impacting both air quality and public health. Mobile monitoring of HCHO allows for accurate source attribution and effective emission control strategies; however, this necessitates instruments with rapid response, high sensitivity, and robustness under mobile operation conditions. This work presents a robust mid-infrared wavelength modulation spectrometer for HCHO measurement. A compact modified Chernin cell with a path length of up to 120 m at 50 cm optical base length was developed to improve detection sensitivity. Real-time rapid background subtraction was implemented to eliminate spectral background structures. Laser current jitter was employed to suppress optical interference fringes and vibration-induced noise. The developed spectrometer achieved a detection limit of 0.89 ppbv with an averaging time of 1 s, corresponding to a detection sensitivity of 3.1 x 10(-9) cm(-1). The spectrometer demonstrates high robustness and offers a reliable solution for precision mobile HCHO monitoring.

High-entropy glass materials are gaining attention because they combine useful properties for energy, electronic, and biomedical applications. Building on crystalline high-entropy alloys, the introduction of amorphous multi-component structures opens new ways to tune material properties, much like metallic glasses did in the past. This review discusses how high-entropy metallic, oxide, and organic glasses form, focusing on entropy stabilization, structure–property relationships, and advanced processing methods. Despite recent breakthroughs—such as ultra-hard oxide glasses and high-performance catalytic organic systems—the field still faces challenges in understanding non-configurational entropy contributions (electronic, magnetic, and vibrational) that affect phase stability. Tackling these theoretical issues is essential for moving beyond empirical design toward a rational, entropy-driven approach for developing next-generation glass materials in metallic, ceramic, and polymeric systems.

Agricultural soil is a major source of atmospheric nitrogen oxides (NOx), but in situ NOx flux measurements remain sparse and unevenly distributed, limiting mechanistic understanding of soil NOx emissions and introducing substantial uncertainties in emission estimates. In this study, an aerodynamic gradient (AG) system utilizing broadband cavity-enhanced absorption spectroscopy was deployed for nitrogen dioxide (NO2) flux measurements in a Huai River Basin wheat field. Following quality control involving stationarity and concentration gradient tests, 54.5% of the measurements were retained. An eXtreme Gradient Boosting model incorporating NO2 fluxes and 11 drivers was constructed to impute missing values. It demonstrated strong performance, achieving a correlation coefficient of 0.97 and root mean square error of 18.16 μg N m−2 h−1 on the training set, and values of 0.83 and 38.60 μg N m−2 h−1 on the test set. The resulting mean gap-filled NO2 flux was 49.95 μg N m−2 h−1, indicating the field to be a net NO2 source, while estimates based on original data overestimated the flux by 11.2%. Machine learning analysis showed that net radiation, ambient NO2 concentration, friction velocity, carbon monoxide, and ozone were key drivers, suggesting that NO2 fluxes primarily originate from photochemical oxidation of soil-emitted nitric oxide, simultaneously influenced by wheat canopy. Based on the mean flux and wheat cultivation area, wheat fields in the Huai River Basin were estimated to contribute approximately 21.95 Gg N yr−1 to atmospheric NO2. This study provides an important basis for optimizing the AG-based flux, accurately estimating soil-derived NO2 fluxes, and deepening the understanding of underlying mechanisms.

Heat-not-burn tobacco products (HTP) as alternatives to traditional cigarettes could reduce the release of harmful components in tobacco smoke by avoiding high-temperature combustion. However, detailed chemical analysis of the gas-phase HTP smoke is necessary because tobacco pyrolysis is the primary source of certain hazardous volatile organic compounds (VOCs). In this study, a vacuum ultraviolet time-of-flight photoionization mass spectrometer is combined with Hefei synchrotron radiation to analyze gas-phase HTP smoke online at the molecular level. A large number of VOCs have been observed online and assigned in photoionization mass spectra. The mass-selected photoionization efficiency (PIE) spectra of the major VOC species were measured by scanning synchrotron photon energy and fitted well to structure-specific molecular photoionization cross sections (PICS). The structures of species in the gas-phase HTP smoke are determined, and abundant isomers are differentiated. The present results demonstrate that despite avoiding high-temperature combustion processes, HTP still generates various hazardous VOCs through tobacco pyrolysis, including toxic or carcinogenic carbonyl compounds, unsaturated hydrocarbons, heterocyclic compounds, and sulfides. Their impact on human health and the environment requires further analysis. These findings provide in-depth, isomer-specific insights into our understanding of the exposure risks from HTP smoke and are crucial for guiding future regulation of HTP.

A novel broadband, high-resolution spectroradiometer based on a virtually imaged phased array (VIPA) has been developed to meet the stringent requirements for high-precision vertical profiles of key atmospheric constituents. The instrument operates within the spectral range of 7535-7680 cm-1, achieving a spectral resolution of 0.023 cm-1 (690 MHz) with an integration time as short as 400 ms. Using this system, high-resolution atmospheric transmittance spectra in the 7535-7680 cm-1 band were successfully measured, and the vertical profile of water vapor was retrieved using the optimal estimation method (OEM). The results demonstrate that the novel VIPA-based spectroradiometer enables rapid acquisition of high-resolution atmospheric transmittance spectra over a broad spectral range, providing a robust and effective new approach for remote sensing of key atmospheric constituents. To the best of our knowledge, this represents the first successful application of a VIPA-based spectroradiometer for retrieving vertical profiles of atmospheric constituents.

ABSTRACT Ce:LuAG ceramic phosphors are promising green phosphor conversion materials for high‐brightness lighting and display. However, despite its excellent resistance to thermal quenching, Ce:LuAG still suffers from thermal drop of the luminescence under high‐power excitation, particularly under ultra‐high‐brightness laser excitations. This work investigated the effects of excessive Al 2 O 3 addition to the Ce:LuAG ceramic phosphor combined with vacuum brazing on the luminescence thermal stability. Experimental results indicate that 10 wt.% Al 2 O 3 addition improves the Ce:LuAG ceramics microstructure, thermal conductivity, and in result enhances the comprehensive luminescence performance. Cross‐sectional BSE and EDS analysis reveals a dense, crack‐free brazed interface with Ti enrichment at the ceramic/braze boundary, confirming the formation of a Ti‐O reaction layer that enables chemical bonding and efficient heat dissipation. The sample with an additional 10 wt.% Al 2 O 3 brazed at 870°C achieves light conversion efficiency of 253 lm·W −1 at an excitation light power of 2 W, with light conversion efficiency drop of only 10% at a light power of 8 W. (For the samples without additional 10 wt.% Al 2 O 3 , the light conversion efficiency drop exceeds 15.5% at an excitation light power of 8 W.) With light output exhibiting good linear correlation with excitation blue laser power across the 0–30 W range ( R 2 = 0.99784). The illuminance of the ceramic increased linearly within the 10–80 W range, the brazed sample at 870°C reached 2.05 × 10 4 lx under a light excitation power of 90 W, exhibiting better luminescence thermal stability than the Ce:LuAG ceramic phosphors without excessive Al 2 O 3 addition. The combination of excessive Al 2 O 3 addition and vacuum brazing is an effective solution for achieving robust luminescence from Ce:LuAG ceramic phosphors toward high‐power laser excitations.

The hydroperoxyl radicals (HO2) play a crucial role in atmospheric chemistry. Direct in-situ measurement of HO2 concentration using laser spectroscopy has always been a challenge, requiring very high detection sensitivity. In this presentation, we report the development of a frequency-stabilized cavity ring-down spectrometer (FS-CRDS) for the direct measurement of HO2 concentration. The optical cavity of the spectrometer was made of perfluoroalkoxy (PFA) tube with an inner diameter of 9 mm. The distance between the two high reflectivity mirrors (double coated, with reflectivity R = 95% at λ = 632 nm and R = 99.998% at λ = 1506 nm) was about 51.4 cm, with one of the cavity mirrors mounted on a piezo-electric transducer (PZT). A stable red He-Ne laser with a frequency stability of ±2 MHz was used as the reference laser for the cavity length stabilization servo. A 1506 nm fiber laser was used as the probe laser. The probe laser beam was split into two beams: one beam was used to lock the probe laser to the stable cavity using Pound-Drever-Hall (PDH) locking method; the other beam passed sequentially through an acousto-optic modulator (AOM) and a fiber electro-optic modulator (EOM) for cavity ring down spectroscopy (CRDS) measurement. By tuning the frequency of the microwave source drive of the EOM, and using a frequency-agile, rapid scanning spectroscopy method, the laser sidebands were sequentially switched to different optical cavity models, thereby achieving rapid full-spectrum scanning. With a 1 s integration time, the spectrometer achieved a detection sensitivity of about 2.6×10-11 cm-1, which was about 12 times improved compared with normal CRDS system without electronic locking. The corresponding detection limit for HO2 radicals was about 1.2×108 molecule/cm3 (the absorption line for HO2 detection was located at 6638.207 cm-1, with a line strength of 7.09 × 10-21 cm-1/(molecule cm-2)). This work demonstrates that FS-CRDS is a feasible technique for high sensitivity direct measurement of HO2 radicals. Further improvements will be made in the future to enhance detection sensitivity.

Secondary organic aerosols (SOAs) formed via the photooxidation of toluene and other aromatics are major components of fine particles. A synchrotron radiation vacuum ultraviolet photoionization aerosol mass spectrometer (VUV-PIAMS) was used to conduct online detection of the components of SOA generated by toluene chamber simulation in this study. Mass spectra of SOA particles were measured at a photon energy of 10.5 eV. The photoionization efficiency (PIE) curve of each ion peak within the 7.5-11.5 eV range was obtained, and then the qualitative analysis based on ionization potential (IP) was utilized to determine the composition of SOA. Experimental results demonstrated that mass spectra of toluene SOA primarily contained peaks at m/z = 64, 72, 94, 106, 108, and 122, with IPs of 8.92±0.03, 9.63±0.03, 8.53±0.03, 9.45±0.03, 8.28±0.03, 8.93±0.03, and 9.26±0.03 eV, respectively. Combined with theoretical calculations and offline measurements of ultraviolet-visible absorption spectroscopy and electrospray ionization mass spectrometry, it was determined that furan, methylglyoxal, phenol, benzaldehyde, 2-methylphenol, 4-methylphenol, and benzoic acid were the major components of toluene SOA. Based on the areas of the mass peaks, methylphenol, benzaldehyde, benzoic acid, methylglyoxal, phenol, furan, and unidentified components accounted for 21.4%, 17.1%, 15.7%, 14.3%, 12.9%, 11.4% and 7.2% of the measured components, respectively. The obtained results provide new information for studying the photooxidation mechanism of toluene. VUV-PIAMS overcomes cumbersome sample preparation procedures, potential secondary contamination, and other shortcomings of offline measurements, making it a useful tool for measuring the compositions of SOA and revealing their formation processes.

Spontaneous, radical-mediated oxidation of nicotine has been demonstrated to occur at nanometer aerosol interfaces under ambient conditions for the first time. The oxidation products were identified by vacuum ultraviolet photoionization aerosol mass spectrometry, whereas peroxy-radical adducts were detected by electron paramagnetic resonance spectroscopy, providing direct evidence for radical-mediated oxidation at the air-water interface of aerosols. The oxidation was markedly inhibited by sodium chloride and benzoic acid: the former attenuates interfacial electric fields that promote hydroxyl radical generation, whereas the latter forms a stable complex with nicotine, blocking reactive sites for hydrogen abstraction. These findings reveal a previously unrecognized transformation pathway for nicotine, clarifying its degradation under humid respiratory conditions while also uncovering a general interfacial mechanism for spontaneous oxidation of organic species confined in aqueous aerosols.

Nitrophenols (NPs) components of atmospheric secondary organic aerosol (SOA) have strong light absorption ability and toxicity, which exacerbate haze pollution and endanger human health. The formation of SOA particles by atmospheric chemical processes of aromatic compounds in presence of sodium nitrate (NaNO3) fine particles are simulated in current study. Chemical components and optical properties of NPs are characterized using mass spectrometer and spectroscopic instruments. The on-line measurement of aerosol laser time-of-flight mass spectrometer and verification by electrospray ionization mass spectrometer demonstrate that nitrophenol, dinitrophenol, nitro-dihydroxybenzene, and dinitro-dihydroxybenzene are major NPs products for aromatic SOA in presence of NaNO3 fine particles. Also, these aromatic SOA particles possess fluorescence characteristics, and they exhibit the highest fluorescence intensity at 398 nm when excited by 363 nm ultraviolet light. Averaged mass absorption coefficient () of SOA in 200-600 nm is between 279 and 512 cm2/g, indicating strong absorption ability. Comprehensively considering the steric hindrance and electron donating effects of substituents for methyl and ethyl, mass concentration, and the emitted 398 nm fluorescence intensity of aromatic SOA particles exhibit the pattern of benzene > ethylbenzene > toluene > p-xylene >1,2,4-trime-thylbenzene. These provide experimental references for studying chemical composition and optics of NPs in anthropogenic SOA.

The Tibetan Plateau (TP), as one of the most sensitive regions to climate change, exerts significant impacts on regional climate patterns. Recent studies have observed unexpectedly strong aerosol absorption on the TP, leading to positive direct aerosol radiative forcing at the top of the atmosphere (DARFTOA) and potentially accelerating TP warming. However, light absorption by different aerosols remains poorly quantified, especially when considering the influence of dark-brown carbon (d-BrC), which exhibits characteristics similar to black carbon (BC). Based on size-resolved aerosol chemical compositions and optical properties measured on the TP, this study proposes a novel framework to derive aerosol absorption contributions by BC, the lensing effect, methanol-soluble organic aerosols (MSOA), and d-BrC. Contrary to expectations, approximately 50-70% of aerosol absorption across the 405-780 nm wavelength range is attributed to d-BrC in Lulang and Lhasa, rather than BC. DARFTOA changes from +2.83 to -0.42 W/m2 when absorption by d-BrC is excluded. These results reveal that d-BrC is a key factor determining aerosol warming or cooling effect on the TP, and it should be incorporated into weather and climate models for improving the assessment of aerosol radiative forcing. Dark brown carbon is usually overlooked in evaluating aerosol radiative effects. This study demonstrates that dark-brown carbon contributes more than 50% of aerosol absorption on the Tibetan Plateau.

All-optical computing offers ultra-high speed, low-power consumption, and parallel processing capabilities, crucial for overcoming Moore's Law limitations. However, conventional single-wavelength diffractive deep neural networks (D2NN) face significant challenges in achieving synergistic optimization between high-precision optical edge-feature extraction and classification tasks. Here, an edge-detecting spin-differential diffractive neural network (ESD-DNN) is proposed for single-wavelength all-optical object classification. The network architecture is implemented through a Pancharatnam-Berry phase gradient metasurface to achieve rapid edge-feature extraction, while classification inference is accomplished by utilizing a spin-differential mechanism based on left-/right-handed circularly polarized (LCP/RCP) components. Through end-to-end optimization of the diffractive layers, the ESD-DNN achieves co-optimization of edge-feature extraction and classification, significantly improving accuracy while reducing computational costs. Numerical validations reveal that the single-layer ESD-DNN attains 97.5% (MNIST) and 87.5% (Fashion-MNIST) classification accuracy, surpassing traditional single-wavelength D2NN by 10.2% and 5.2%, respectively. Meanwhile, it achieves 5-fold higher computational efficiency while reducing time complexity by 80% compared to a four-layer D2NN. Remarkably, under extreme conditions such as moderate turbulence intensity or thermal lensing effects, the network maintains >90% classification accuracy (MNIST), demonstrating its exceptional environmental robustness. These findings pave the way for applications in artificial intelligence, satellite remote sensing, intelligent industrial inspection, and space optical communications.

Detecting and identifying bioaerosols in the atmosphere is important for applications related to human health and public safety. Recently, single-particle aerosol mass spectrometry has been increasingly used for the detection of bioaerosols. However, it encounters challenges including difficulties in transmitting large-size aerosol particles and interference from non-biological aerosols in the atmosphere. In this study, a singleparticle aerosol mass spectrometer was improved by extending the upper particle size transmission limit and integrating a fluorescence-based particle screening function. The fluorescence signal detection module was used to select particles exhibiting intrinsic laser-excitable fluorescence, thereby reducing data acquisition from nonbiological aerosols. Simulation and experimental results indicate that the optimized instrument enables transmission of particles with diameters up to 5 mu m, making it more suitable for bioaerosol transmission and analysis. Performance metrics show that the misidentification rates of the instrument for background particles, sodium chloride (NaCl) and ammonium sulfate ((NH4)2SO4), are 0.12% and 0.16%, respectively, while the identification rate for fluorescent polystyrene latex microspheres (PSLs) particles is 88.4%. Laboratory experiments using mixed solutions of NaCl and fluorescent PSLs verify the instrument's capability to select fluorescent particles by analyzing the corresponding particle size information and mass spectral data.

beta-ocimene ozonolysis represents an important atmospheric source of secondary organic aerosols (SOA), yet its transformation pathways and kinetics are not fully understood. Here, vacuum ultraviolet photoionization time-of-flight mass spectrometry (VUVPI-TOFMS) combined with high-level theoretical calculations is employed to elucidate its oxidation network. Twenty-five gas-phase oxidation products are directly detected in the mass spectra, including ozonides, bicyclic epoxides and peroxy radical-derived species. The reaction rate constant for beta-ocimene + O-3 is theoretically calculated as 3.89 & times; 10(-16) cm(3) molecule(-1) s(-1) at 298 K, in good agreement with available experimental data. Our results show that ozone reacts predominantly (>87%) at the allylic double bond of beta-ocimene, forming C7H10O + (CH3)(2)COO, anti-C7H10O2 + (CH3)(2)CO, and syn-C7H10O2 + (CH3)(2)CO products with branching ratios of 0.71, 0.28, and 0.01, respectively. Then the syn-C7H10O2 Criegee intermediate undergoes competing bicyclic ring-closure (3.22 & times; 10(5) s(-1)) and H-shift reactions (2.96 & times; 10(4) s(-1)), while the anti-C7H10O2 conformer mainly undergoes a bicyclic ring-closure reaction (3.27 & times; 10(2) s(-1)). An autoxidation route via C7H9O3 peroxy radicals is also identified, proceeding through cyclization coupled with H-shift (1.67 s(-1)) to generate highly oxygenated species. These integrated mechanistic and kinetic insights elucidate previously uncertain chemistry of Criegee intermediate and peroxy radicals, and thus enhance our understanding of the formation of monoterpene-derived secondary pollutants.

Nitrate is an important inorganic aerosol component that can affect the formation and optical properties of nitro-polycyclic aromatic hydrocarbons (NPAHs) present in secondary organic aerosols (SOAs). Sodium nitrate (NaNO3) was selected as a representative nitrate, and the atmospheric chemical process for naphthalene photooxidation to generate SOA in the presence of NaNO3 particles was investigated using a smog chamber system. NPAH components were measured online using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) and offline using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), electrospray ionization mass spectrometry (ESI-MS) and quantum chemical calculations. The optical parameter of the averaged mass absorption coefficient (〈MAC〉) of SOA was detected using a UV-visible absorption spectrometer and an organic carbon analyzer. The experimental results demonstrated that NaNO3 particles promote the formation of SOA and generation of NPAH components. Compared with the results of previous experiments on naphthalene photooxidation, 2-nitronaphthalene, 2,4-dinitronaphthalene, 2-nitro-1-naphthol, 2,4-dinitro-1-naphthol, 1,3-dihydroxy-2-nitro-naphthalene and 1,3-dihydroxy-2,4-dinitro-naphthalene were determined as the main components of SOA in the presence of NaNO3 particles. The reaction energy and Gibbs free energy change for the formation of 2-nitronaphthalene were the largest among all the reactions. 2-Nitronaphthalene was the main NPAH product. Naphthalene and its gaseous photooxidation products condensed and reacted on NaNO3 particles' surface to yield NPAHs with intense light absorbability, resulting in a significant increase in the 〈MAC〉 of SOA. The 〈MAC〉 of naphthalene SOA steadily increased with increasing NaNO3 particles' concentration. The 〈MAC〉 for naphthalene SOA in the presence of 100 µg m-3 NaNO3 particles was 645 cm2 g-1, slightly less than the 〈MAC〉 of organic aerosols from biomass burning (700 cm2 g-1). This study provided the experimental basis for source identification and light absorption characteristic study of NPAH components in atmospheric SOA in the presence of NaNO3 particles.

The effects of modulating oxygen vacancies via sintering in oxygen on the (0.8-x) TiO2-xZrO(2)-0.2Cu(1/3)Nb(2/3)O(2) (0 <= x <= 0.4) ceramics have been systematically investigated in terms of microstructure, electrical conductivity, and dielectric properties. Zr4 + doping is found to induce a phase transition from rutile to srilankite, accompanied by the distortion of Ti-O octahedra. An oxygen atmosphere remarkably promotes grain refinement, inhibits Ti4+ reduction and suppresses the oxygen vacancy formation. Notably, the 0.45TiO(2)-0.35ZrO(2)-0.2Cu(1/3)Nb(2/3)O(2) ceramic sintered in oxygen achieves a substantial 58% enhancement in its quality factor compared to its air-sintered counterpart, delivering excellent dielectric properties: epsilon(r) similar to 38.4, Q & times; f similar to 17527 GHz, and tau(f) similar to -6.9 ppm/degrees C. The remarkable improvement in Q & times; f value can be attributed to the synergistic effect of higher bulk density, Ti-O octahedral distortion, and a reduction in defects like oxygen vacancies. Moreover, the measured dielectric properties are highly consistent with intrinsic characteristics via measuring and fitting the far-infrared spectra. This work offers an effective strategy for improving the performance of dielectric ceramics for next-generation wireless communication applications.

Objective Formaldehyde (HCHO) is an important air pollutant in both indoor and outdoor environments. Its emission sources include the direct releases from industrial emissions, construction materials, and polymeric resin-based furnishings. HCHO can also be generated through the photochemical oxidation of volatile organic compounds (VOCs) in atmospheric environments. Accurate measurement of formaldehyde concentration is crucial for health effect studies, atmospheric chemistry research, and pollution prevention. Tunable diode laser absorption spectroscopy (TDLAS) is one of the important methods for detecting formaldehyde, which offers advantages such as high sensitivity, high time resolution, and in-situ measurement. However, temperature variation in the operating environment can affect the key parameters of a TDLAS system, thereby impacting system stability and measurement sensitivity. To address this issue, two primary temperature control methods are usually employed. One involves directly controlling the temperature of the multi-pass gas cell (MPC) to maintain optical path length stability. The other entails temperature control of the entire optical path of the TDLAS system, including the multi-pass cell, laser, photodetector, mirrors, and lenses. Temperature control has been demonstrated to be an effective means to improve the performance of TDLAS systems. However, precise temperature control specifically tailored for formaldehyde measurement systems has not been reported before. Methods A TDLAS system with optical path temperature control is developed for formaldehyde measurement. The instrument uses a mid-infrared interband cascade laser emitting at 3.5 mu m as the probe source. The absorption line of formaldehyde is selected at 2831.64 cm-1 with a line strength of S=5.651>< 10(-20) cm(-1)/(moleculecm(-2)). A compact dense spot pattern spherical mirror cell is developed with an optical base length of 17.7 cm, which allows the incident laser beam to reflect 312 times in the multi-pass cell, thereby increasing the effective absorption path length to 55.2 m, with a volume of only 350 mL. The Gaussian beam formula is used to fit the beam radius at different distances to obtain the beam waist position. A focusing lens (f=500 mm) is employed to adjust the beam waist position. The laser beam waist is matched to the center of the multi-pass cell, which is located 479 mm away from the laser. To enhance measurement precision, wavelength-modulated spectroscopy (WMS) and rapid background subtraction techniques are used to minimize the noise in the spectral signal. A semiconductor cooling temperature control box is developed to maintain the operating temperature of the optical system at 32 degrees C. Results and Discussions The temperature inside the temperature control box could be stabilized at 32 degrees C with a high precision of 6 m degrees C (Fig. 6) when the temperature control is turned on. Rapid background subtraction is performed using a three-way solenoid valve, which enables swift switching between the background gas and sample gas. The total time consumed to complete a background subtraction measurement is 16 s. The sample gas signal is difficult to distinguish accurately due to interference from background structures. However, by subtracting the background gas spectrum, the 2f signal can be extracted, which significantly improves the detection sensitivity of the system (Fig. 7). During calibration, the absolute concentrations of diluted HCHO gas in the cell are calculated using direct absorption spectroscopy. The peak-to-peak value of the formaldehyde 2f signal exhibits a linear relationship with volume fraction, which yields a correlation coefficient of 0.9994 (Fig. 8). The performance of the TDLAS instrument is evaluated by measuring a time series of formaldehyde concentrations at a fixed volume fraction. With temperature control enabled, the system achieves a detection precision of 0.25>< 10-9 (1 sigma, 60 s), which is 4.7 times higher than that when temperature control is disabled (Fig. 10). Conclusions The system utilizes a compact, dense spot pattern spherical mirror optical multi-pass cell with a path length of 55.2 m and a volume of only 350 mL to enhance the effective absorption path. The beam profile of the used interband cascade laser emitting at 3.5 mu m is measured, and the laser beam waist is matched to the cell. A semiconductor-based thermoelectric temperature control box is designed to precisely regulate the entire optical path, including the interband cascade laser, multi-pass cell, and detector, which achieves a temperature control precision of 6 m degrees C at the set point of 32 degrees C . By combining wavelength modulation spectroscopy and rapid background subtraction techniques, the system achieves a measurement precision of 0.25x10(-9) (1 sigma, 60 s) under temperature-controlled conditions, which is 4.7 times higher than that under non-temperature-controlled conditions.

An ideal data acquisition and processing system has the characteristics of high integration, low latency, wide applicability, and scalability. Its development plays a vital role in the advancement of optical instruments. Most of the data acquisition and processing systems currently used are based on digital signal processing (DSP) or system-on-chip (SoC) architectures, which are limited in processor performance, number of interfaces, and edge computing capabilities. In this presentation, we report a data acquisition system (SOM-FPGA lock-in, SFLI) based on modular system-on-module (SOM) and field-programmable gate array (FPGA) architecture. The SFLI system integrates high-speed signal acquisition and processing, digital lock-in amplifier (DLIA), and edge data storage functions, improves the edge computing capability of the system, and has the advantages of high performance, multiple interfaces, and low cost. The system can simultaneously achieve four-channel high-speed acquisition (sampling rate up to 65 MSPS) and digital phase sensitive detector (demodulation frequency from DC to 5 MHz). When the modulation frequency is 20 kHz and the input voltage range is 1 V, the input voltage noise of the SFLI system is about 41 nV/√Hz. The performance of the SFLI system is compared with that of a commercial lock-in amplifier, showing good consistency. The SFLI has been applied to cavity-enhanced spectroscopy technology, providing a new solution for the miniaturization of optical instruments and edge computing in practical applications.

Vertical detection of volatile organic compounds (VOCs) is essential to expend our understanding of the distribution characteristics of VOCs and improve the predictive ability of existing air quality models. In this work, we report the development of a sorbent tube sampler based on an unmanned aerial vehicle (UAV) platform. Vertical profile measurement of VOCs with a vertical resolution of 25 m was achieved. The sampler consists of five lightweight VOC sorbent tubes and a 5-way solenoid valve, making it available for collecting five atmospheric VOC samples in a single flight with a time response of less than 30 min. The sampler weighed similar to 1.45 kg and had dimensions of 240 mm x 220 mm x 100 mm with small penetration loss (<10%) under 4-liter sampling conditions (flow rate of 200 mL/min). Commercialized SUMMA canisters were used as experimental controls to investigate the possible loss of self-made sampler for target compounds in the same sampling process. Comparison experiment on the ground showed that the concentration differences for all VOC species were lower than 0.14 mu g/m(3), proving the good reliability for VOCs measurements using sorbent tube sampler. The UAV platform also incorporated online instruments for meteorological parameters and O-3 measurement. The sampler was successfully applied to characterize the vertical profiles of VOCs up to 100 m in October 2023 in the Huaihe River Basin of China. The UAV platform and the sorbent tube sampler demonstrate good performance and will be a valuable and reliable tool for vertical VOCs measurement. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.