Journal of Quantitative Spectroscopy & Radiative Transfer最新文献

A comprehensive understanding of the nature of light-induced plasmonic nanobubbles (PNBs) generated around noble metal nanoparticles is essential for optimizing PNB-based applications, such as light-driven microfluidic control. To investigate the overall evolution pattern of plasmonic nanobubbles (PNBs) under continuous light illumination, a computational model based on the least-squares method is established. Meanwhile, the variations in nanofluid transmittance and vaporization mass under continuous light illumination are measured by an immersion fiber and an electronic balance, respectively. The effects of nanoparticle concentration on the nanofluid transmittance and vaporization mass are analyzed. Considering the variations in nanofluid concentration, the overall evolution pattern of PNBs is preliminarily analyzed by monitoring the real-time dynamic change in nanofluid transmittance. The experimental results indicate that the nanoparticle concentration has an important effect on the nanofluid vaporization process. During the illumination stage, an increased nanofluid concentration intensifies the synergistic effect of water vaporization and PNB growth on transmittance reduction. The change in nanofluid transmittance caused by PNB scattering greatly exceeds that caused by increasing nanoparticle concentration. The nanofluid concentration gradually increases and peaks at the end of the cooling stage, and the rate of change of the nanofluid concentration is proportional to the nanofluid concentration. The numerical calculations show that the average size and the range of the PNB size distribution continuously increase with increasing irradiation time, and decrease during the cooling stage. A higher nanofluid concentration corresponds to a wider range of PNB size distribution.

We identify two metastable excited states in Sm${}^{10+}$ highly charged ion as candidates for high accuracy optical clocks. Several atomic properties relevant to optical clock development are calculated using relativistic many-body methods. This includes energy levels, transition amplitudes, lifetimes, scalar polarizabilities, black body radiation shift, and the sensitivity to the fine structure constant variation. We found that the clock transitions are not sensitive to perturbation, e.g., relative black body radiation shifts are $\sim 10^{-19}$. The enhancement factor for the $\alpha$ variation is $\sim$ 0.8 for one clock transition and $\sim$ 16 for another.

This paper report nitrogen- and oxygen-broadening coefficients, their speed-dependencies, and the collisional narrowing parameters of lines in the ν₄-band of methane. The parameters were determined from low (150 K) to high temperatures (600 K). The measurements were done with a high-resolution quantum cascade laser spectrometer coupled to specific absorption cells that allow to cool and heat the gas mixtures with a great stability. The spectroscopic parameters were determined at each temperature by fits of the experimental absorbances in a multispectrum fitting procedure using the Voigt, Speed-Dependent Voigt, Nelkin-Ghatak and Speed-dependent Nelkin-Ghatak theoretical line shape models. The temperature dependencies of the collisional half-widths, the speed-dependence of the broadening coefficients as well as the collisional narrowing parameters were studied with the empirical power law and the physics-based Gamache-Vispoel model (DPL) [Gamache and Vispoel, JQSRT, 217, 440–452, 2018]. The obtained line shape parameters and their temperature dependencies are compared, when possible, to existing data in literature. The DPL reproduces more accurately the evolution of the studied collisional parameters over the wide range of temperature considered in the study.

Following previous contributions dedicated to the main isotopologue, ¹⁴NH₃, in the present work, we examine the ¹⁵NH₃ absorption spectrum between 3950 and 6350 cm^-1 in order to elaborate an absorption line list for ammonia in natural isotopic abundance. For this purpose, several room temperature Fourier Transform absorption spectra of ammonia highly enriched in ¹⁵NH₃ measured in the 90′s and available from the Kitt Peak data centre have been analysed. In addition, a more recent high-resolution spectrum recorded in Brussels between 4150 and 4600 cm^-1 is also considered. The spectra were divided in three separate intervals (3900–4706, 4706–5650 and 5650–6350 cm^-1) for which experimental lists including 3506, 3788, and 2317 lines, respectively, were retrieved and treated independently. By comparison with an ab initio line list (the BYTe list) and systematically validating the assignments by using lower state combination difference relations (LSCD), 2013, 1771 and 570 transitions could be assigned in the three regions, respectively. They belong to 16, 22, and 10 bands and correspond to 98.5, 92.6 and 78.6 % of the experimental intensities in the region, respectively. For comparison, only four ¹⁵NH₃ bands were previously assigned in the literature in the entire studied region.

The obtained ¹⁵NH₃ assigned line lists were gathered with the previously elaborated line list of the main isotopologue to produce a recommended line list for natural ammonia between 3900 and 6350 cm^-1.

The complexity of the rocket motor exhaust plume radiation phenomenon, along with the influence of numerous parameters and implicit propagation, makes the theoretical simulation calculations expensive. This hinders design optimization, parameter identification, and other studies. Hence, it is crucial to establish the direct correlation between thrust, velocity, altitude, detection angle, and plume radiation in engineering.

The paper proposes a scaling law modeling approach for predicting plume infrared radiation from liquid oxygen (LOX)/kerosene rocket engines to solve the difficulties of quick prediction and lack of explicit models. An explicit scaling law model with four parameters is developed by utilizing the e-exponential scaling law to relate plume radiance to flight velocity, the power scaling law to relate plume radiance to vacuum thrust, and the sinusoidal scaling law to relate plume radiance to detection angle. This model employs a decoupled modeling approach for plume radiance, flight altitude, flight velocity, vacuum thrust, and detection angle. A fast prediction method for the LOX/kerosene rocket engine plume in the altitude range of 11∼61 km is achieved. The theoretical simulation test shows the relative error of the velocity-scaling law in predicting the radiance of the RD-180 template engine during the Atlas III flight trajectory is less than 20 %. The radiance of the RD-170 and RD-191 rocket engines is predicted using the thrust-scaling law based on the radiance of the RD-180 template engine exhaust plume. The radiance of the exhaust plume from the RD-170 and RD-191 rocket motors is estimated using the thrust-scaling law with an accuracy of under 15 %. Subsequently, the radiance of these two motors at detection angles between 10° and 170° is predicted using the angle-scaling with a relative error of less than 35 %.

We showcase a Raman scattering diagnostic for 2D imaging of the rotational and vibrational temperatures of H₂. Applications include environments with vibrational-rotational non-equilibrium such as H₂-containing supersonic jets and plasma reactors. We image segments of the laser scattering spectrum, containing one or more Raman features, using an ICCD camera that is equipped with one of several bandpass filters. Knowing their transmission spectrum allows the construction of calibration curves that relate the relative intensities of the multi-spectral image to the rotational and vibrational temperatures. Additionally, the absolute intensity indicates the density of H₂. We illustrate the capability to independently measure rotational (300–3000 K, $\pm$150 K) and vibrational temperatures (1000–3000 K, $\pm$50 K). The technique is demonstrated on two different H₂ microwave plasmas and validated against conventional fitting of 0D and 1D Raman spectra.

This paper presents comprehensive spectral measurements and a theoretical analysis of laser-produced germanium (Ge) plasma within the 7.5–17 nm wavelength range, with the measurements being performed using spatiotemporally-resolved emission spectroscopy. We obtained and analyzed the extreme ultraviolet (EUV) spectra and their variations meticulously at various positions adjacent to the target surface. The 3p and 3d excitations of Ge ions spanning from Ge⁴⁺ to Ge¹³⁺ were calculated using the Cowan configuration interaction codes, with particular emphasis being placed on analysis of the spectral line distributions in the 3d-np, 3d-nf, and 3p-3d, 4s, 4d transition arrays. This analysis indicated the contributions made by these transition arrays to the broadband spectral features that were observed experimentally. By using a steady-state collisional radiation model along with a normalized Boltzmann distribution assumption, we clarified the predominant contributions of the 3d-4p and 3p-3d transitions from the Ge⁷⁺ to Ge⁹⁺ ions in close proximity to the target surface, along with those from the Ge⁵⁺ and Ge⁶⁺ ions at greater distances. Furthermore, by combining the results above with a plasma dynamics evolution analysis, we gained insights into how the plasma's transient and nonuniform properties influence the analysis of complex EUV band spectral profiles and examine their implications for spectral diagnostics. These results will be useful for plasma spectral diagnosis and for application to development of pulsed short-wavelength light sources.

This study presents a new experiment to measure the polarization-resolved two-dimensional light-scattering patterns, near and including the backscattering direction, of fixed particles representative of some atmospheric-aerosol types. The measurements are conducted across a broad spectrum, from 450 to 850 nm, and for different polarization states. A supercontinuum laser, achromatic optics, and polarizers are used to measure the scattering patterns. Important quantities for applications such as lidar are also measured including the backscattering phase-function and the linear depolarization ratio in the exact backscattering direction. Microscopic images of the particles are provided by digital in-line holography as well. Thus, in some cases, it is possible to interpret the spectro-polarimetric measurements with knowledge of the size and shape of the particles involved. Spherical particles of known properties are used to calibrate the method. Then, Arizona test dust, Gobi and Sahara Desert dust, and ash from the Eyjafjallajökull and La Palma volcanic eruptions are studied to illustrate the method's potential for lidar applications.

We introduce CaSDa24, the latest iteration of our high-resolution molecular spectroscopy database cluster. Comprising ten independent databases, each dedicated to a specific molecule (CH₄, CH₃Cl, SF₆, C₂H₄, CF₄, GeH₄, RuO₄, SiF₄, UF₆, SiH₄), CaSDa24 integrates updated and new databases since our previous publication. These databases include detailed lists of calculated spectral lines, eigenvectors, energy levels, and additional relevant information derived from the latest experimental spectra analyses. This article provides an overview of the current state of molecular spectroscopy databases, explains the foundational principles of CaSDa24, and summarizes the significant updates and new data introduced.