Journal of Quantitative Spectroscopy & Radiative Transfer最新文献

{"title":"Mechanism of metastable krypton atom preparation via laser-induced ionization","authors":"","doi":"10.1016/j.jqsrt.2024.109233","DOIUrl":"10.1016/j.jqsrt.2024.109233","url":null,"abstract":"<div><div>Preparation of metastable Kr atoms in the 5s[3/2]₂ level via laser-induced ionization has been achieved. The temporal evolution of the intensity of Kr atomic spectral lines at 760.15 nm, 811.29 nm, and 431.96 nm was used to elucidate the production mechanisms of metastable Kr atoms. These mechanisms primarily involve two processes: the “excitation + radiation” process, dominated by multiphoton excitation and initial plasma-induced electron impact excitation, and the “ion-electron recombination” process, governed by avalanche ionization. The decay time constants of Kr atomic spectral lines, corresponding to the “excitation + radiation” and “ion-electron recombination” processes respectively, were obtained experimentally under both strong and weak ionization conditions. The experiments revealed delay in preparations of metastable Kr atoms between these two processes. To reduce the loss of metastable Kr atoms and effectively utilize their peak concentration, we drew inspiration from metastable rare gas lasers and proposed the “cycling” idea to keep metastable Kr atoms produced by these two processes as synchronized as possible. We used 811.29 nm laser to excite metastable Kr atoms generated rapidly during the “excitation + radiation” stage to the 5p[5/2]₃ level. The Kr atoms returned to the 5s[3/2]₂ level through spontaneous radiation, merging with metastable Kr atoms that were slowly produced during the “ion-electron recombination” stage. We hope that the “cycling” idea can shorten the delay in preparations of metastable Kr atoms from both processes and enhance the peak concentration of metastable Kr atoms. However, the experimental results didn't meet expectations, as we observed a decrease in the 811.29 nm fluorescence after laser excitation, attributed to the accumulation of 5p[5/2]₃ level Kr atoms. These atoms undergo energy pooling to populate the 4d’[3/2]₁ and 5d[7/2]₃ levels, followed by absorption of 811.29 nm laser energy leading to photoionization. Reducing the concentration of 5p[5/2]₃ level Kr atoms helps mitigate the reionization issue.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A physics-informed neural network for non-linear laser absorption tomography","authors":"","doi":"10.1016/j.jqsrt.2024.109229","DOIUrl":"10.1016/j.jqsrt.2024.109229","url":null,"abstract":"<div><div>Hyperspectral absorption tomography has emerged as a promising technique for combustion diagnostics due to its rich spectral measurements. However, the non-linear and ill-posed nature of the inverse problem makes obtaining accurate results challenging. This paper proposes a novel application of a physics-informed neural network to address the non-linear inverse problem in hyperspectral absorption spectroscopy. This method utilizes physical laws and measurement data to guide the neural network in finding the optimal solution, without requiring training data. To demonstrate its capabilities, the physics-informed neural network is employed to retrieve temperature and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> mole fraction fields in axisymmetric laminar diffusion flames via <span><math><mrow><mn>4</mn><mo>.</mo><mn>3</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> TDLAS (tunable diode laser absorption spectroscopy). The developed neural network is applied to resolve the spatial distributions from the spectral dimensions, requiring fewer spatial measurements for directly retrieving temperature and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> mole fraction profiles. We investigate the minimum radial projections needed for accurate retrievals and evaluate the model’s robustness to random noise through the inversion of a simulated flame. The developed model is further applied to reconstruct the temperature and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> mole fraction fields for an experimentally measured flame. Our results demonstrate that the proposed model maintains high retrieval accuracy even with limited, noisy data. This work highlights the potential of the physics-informed neural network for robust solutions to non-linear laser absorption tomography problems in scientific and engineering applications.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measurement of high-temperature absorption cross-sections using an optical cell with a non-uniform temperature distribution","authors":"","doi":"10.1016/j.jqsrt.2024.109243","DOIUrl":"10.1016/j.jqsrt.2024.109243","url":null,"abstract":"<div><div>A mathematical method to enable absorption cross-section measurements using an optical cell with a non-uniform temperature distribution is formulated, validated and experimentally demonstrated in this study. The motivation of the proposed method is to facilitate high-temperature spectroscopic studies in the long-wavelength mid-IR region, and to offer an alternative to highly engineered optical cells. The method is based on virtual segmentation of the non-uniform temperature field within an optical cell into bins, each having a sufficiently uniform temperature. By collecting a set of absorbance measurements corresponding to unique temperature profiles and expressing the temperature dependence of the absorption cross-section in terms of a model with limited number of unknowns, a closed-form system of equations is obtained which can be solved to evaluate absorption cross-sections. It is shown, through a set of simulated validation cases, that modeling the temperature dependence in terms of a third order polynomial results in accurate reconstruction of the cross-section spectra for a wide range of cases. Piece-wise polynomials and an alternative nonlinear model are proposed for improved accuracy and to model potentially complex temperature dependencies of the absorption cross-sections. To demonstrate the application of the proposed method, an optical cell with a non-uniform temperature profile was used to measure the cross-section spectra of methane over 1280 – 1330 cm^-1 at temperatures up to 523 K. The proposed method is expected to be highly useful in collecting spectroscopic data at high temperatures particularly in the mid-infrared region.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A highly efficient Voigt program for line profile computation","authors":"","doi":"10.1016/j.jqsrt.2024.109234","DOIUrl":"10.1016/j.jqsrt.2024.109234","url":null,"abstract":"<div><div>Evaluation of the Voigt function, a convolution of a Lorentzian and a Gaussian profile, is essential in various fields such as spectroscopy, atmospheric science, and astrophysics. Efficient computation of the function is crucial, especially in applications where the function may be called for an enormous number of times. In this paper, we present a highly efficient novel algorithm and its Fortran90 implementation for the practical evaluation of the Voigt function with accuracy in the order of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></math></span>. The algorithm uses improved fits based on Chebyshev subinterval polynomial approximation for functions in two variables. The algorithm significantly outperforms widely-used competitive algorithms in the literature, in terms of computational speed, making it highly suitable for real-time applications and large-scale data processing tasks. The substantial improvement in efficiency positions the present algorithm and computer code as a valuable tool in relevant scientific domains. The algorithm has been adopted and implemented in the Meudon PDR code at Paris Observatory and is recommended for similar applications and simulation packages.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coherent backscattering in discrete random media of particle ensembles","authors":"","doi":"10.1016/j.jqsrt.2024.109226","DOIUrl":"10.1016/j.jqsrt.2024.109226","url":null,"abstract":"<div><div>We consider radiative transfer and coherent backscattering (RT-CB) in a discrete random medium of particles. The elementary scattering matrix of the medium conforms to the ensemble-averaged scattering matrix for nonspherical particles and their mirror particles, both in random orientation. We express the ensemble-averaged matrix, via spectral decomposition, as a linear superposition of four pure Mueller matrices, and enable RT-CB computations via an independent treatment of the pure matrices. We validate the method for sparsely and densely packed random media of spherical particles. For the case of sparse packing, we compare two different RT-CB approaches, one with explicit input of polydisperse spherical-particle characteristics and the other with input by decomposing the ensemble-averaged scattering matrix. The results are in agreement and reproduce markedly well the asymptotically exact results from the Fast Superposition <span><math><mi>T</mi></math></span>-Matrix Method (FaSTMM). For the cases of dense packing, we compare the RT-CB to the FaSTMM by invoking the ensemble-averaged incoherent scattering matrix of volume elements as input for the RT-CB. For non-absorbing particles, the RT-CB agrees well with the FaSTMM. For strongly absorbing particles, there are deviations that underscore the need for further method development. In order to demonstrate the potential of the RT-CB, we compute multiple scattering for a sparsely packed spherical medium of nonspherical feldspar particles by utilizing their experimentally measured ensemble-averaged scattering phase matrix. Finally, we discuss future prospects for the RT-CB.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"StaR-LIF: State-resolved laser-induced fluorescence modeling for diatomic molecules","authors":"","doi":"10.1016/j.jqsrt.2024.109230","DOIUrl":"10.1016/j.jqsrt.2024.109230","url":null,"abstract":"<div><div>This study introduced a new model for quantitative analysis of the state-resolved laser-induced fluorescence signal of diatomic molecules, namely StaR-LIF. This model is built upon a master equation of the collisional-radiative transfer processes, which incorporated the latest data on the collisional energy transfer rates between individual spin- and parity-resolved rovibronic quantum levels, together with the most recent updates on the energy levels, line strengths and broadening/shift parameters of the relevant absorption and fluorescence transitions. To facilitate the use of this model, a web-based graphic user interface has been developed and made available at <span><span>https://starlif.pku.edu.cn</span><svg><path></path></svg></span>. Example applications of the current model have been demonstrated for NO, OH and CH, including parametric studies on the effects of variable pulse width and saturating excitation, as well as the temporal evolution of fluorescence spectrum during collisional transfer. The StaR-LIF model can provide quantitative modeling and analysis capabilities over a wide range of gasdynamic and excitation conditions, and promises to be useful in future LIF studies of complex reacting flows.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretical study of size and shell composition effect of TiO2 core-shell mesoporous microsphere on UV absorption effectivity for photocatalytic application","authors":"","doi":"10.1016/j.jqsrt.2024.109246","DOIUrl":"10.1016/j.jqsrt.2024.109246","url":null,"abstract":"<div><div>Microdispersed photocatalysts based on titanium dioxide (TiO₂) in the form of hollow core-shell microspheres (microcapsules) with mesoporous structure are widely demanded in modern critical technologies related to the catalysis of various chemicals, solving environmental problems, and obtaining cheap fuel. To date, a number of experimental works are known, showing that geometrical parameters of microcapsules (size, shell thickness), as well as microstructural composition (nanosized metal additives, additional inner dielectric core- the \"yolk\") noticeably affect their photocatalytic activity. At the same time, a valuable physical description of the optical properties of porous microcapsules has not been presented in the literature so far. Using the finite element method, we perform a full-wave theoretical simulation of the optical field inside a hollow microsphere whose shell is randomly self-assembled from multiple TiO₂ nanoparticles forming an irregular nanoporous structure. We provide a unified physical explanation of the published experimental data on the optical activity of titanium-dioxide microcapsules and show that the existing theoretical models do not always give a correct interpretation of the observed empirical behaviors.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Br I spectral line measurements in the range 6000–12000 cm‒1: Part II","authors":"","doi":"10.1016/j.jqsrt.2024.109232","DOIUrl":"10.1016/j.jqsrt.2024.109232","url":null,"abstract":"<div><div>The present study uses a high-resolution Fourier Transform Spectrometer to provide data on the spectral line measurements of atomic bromine (Br I) in the 6000 – 12,000 cm^‒1 range in the near-infrared spectral region. Bromine electrodeless discharge lamps (EDL) were prepared and utilized as light sources, while light detectors comprised InGaAs and Si diodes. A total of 302 spectral lines were detected using two different resolutions of 0.008 and 0.009 cm^‒1, unveiling 104 lines reported for the first time. All observed lines have been assigned new center of gravity wavenumber values. We also present the unidentified lines and blended lines that appeared in our spectra. This study provides critical insights and data that enhance the understanding of atomic bromine spectroscopy.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytic results for the electrostatic T-matrix and polarizability of finite cylinders","authors":"","doi":"10.1016/j.jqsrt.2024.109227","DOIUrl":"10.1016/j.jqsrt.2024.109227","url":null,"abstract":"<div><div>The T-matrix for electromagnetic scattering is most commonly computed using the Extended Boundary Condition Method (EBCM), but this approach is numerically unstable for finite cylinders of high aspect ratio. In the electrostatics limit, we show that this instability is caused by catastrophic cancellations in the numerical calculations of oscillatory integrals. We find that the problematic integrals can instead be evaluated by integrating over the complement surface that extends from the cylinder to infinity. The resulting integrals are stable and we are then able to compute the electrostatic T-matrix accurately. The polarizability of the finite cylinder is then derived from this T-matrix and validated against results obtained via discretization. As an alternative, we also investigate the T-matrix on a basis of spheroidal harmonics, which is stable on its own and converges more quickly than on the spherical basis. Since the integrals are analytic, we moreover derive a simple analytic approximation based on truncation of the T-matrix on this basis. Beyond the direct benefits of analytic expressions for the electrostatic cylinder polarizability, this work should pave the way for a stable formulation of the full-wave T-matrix/EBCM approach for cylinders.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A theoretical exploration of the electronic structure and single photoionization of the many-electron system confined in Gaussian potential","authors":"","doi":"10.1016/j.jqsrt.2024.109228","DOIUrl":"10.1016/j.jqsrt.2024.109228","url":null,"abstract":"<div><div>This manuscript investigates the electronic structures, spectral properties, and photoionization processes of the confined atomic system. For this purpose, a relativistic methodology employing the Dirac–Coulomb Hamiltonian within the context of relativistic configuration interaction is suggested, utilizing independent particle basis wavefunctions. The key idea of this approach is to place the atom inside a Gaussian potential, which gives a realistic description of the spatial confinement in quantum dots due to a smooth change at the quantum dot boundaries and has a finite range and depth for the spatial confinement. As a result, the local central potential is modified, which is determined by a self-consistent process. The solutions to the Dirac equation, incorporating the aforementioned central potential, yield both the continuous and bound state wave functions. The photoionization process is determined through the application of the distorted wave approach within the context of relativistic Dirac theory. As an application, the electronic structures of the confined Li atom, including energies, ionization potentials, transition rates, and photoionization dynamical properties such as wave functions, cross sections, and photoelectron angular distributions, are systematically investigated within the dipole approximation for a wide range of potential depths and confining radii. A systematic comparison of the present outcomes is made with other available results. The present study is not only meaningful for fundamental research in atomic and molecular physics, but also has implications for a range of disciplines, such as nanochemistry, materials science, and other related fields.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}