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state of RbCs
摘要： We perform a high-resolution Fourier-transform spectroscopic study of the (4) 1Σ state of the RbCs molecule by applying two-step (4) 1Σ ← A 1Σ+ ～ b 3Π ← X 1Σ+ optical excitation followed by observation of the (4) 1Σ → X 1Σ+ laser-induced fluorescence (LIF) spectra. In many LIF progressions the collision-induced satellite rotational lines are observed, thus increasing the amount of term values and allowing us to estimate the Λ-doubling effect in the (4) 1Σ state. The direct potential fit (DPF) of experimental term values of 777 rovibronic levels of both 85RbCs and 87RbCs isotopologues is performed by means of the robust weighted nonlinear least-squares method. The DPF analysis based on the adiabatic approximation and analytical expanded Morse oscillator potential reveals numerous regular shifts in the measured level positions. The spectroscopic studies of the (4) 1Σ state are supported by the electronic structure calculations including the potential energy curves of the singlet- and triplet-state manifold and spin-allowed transition dipole moments. The subsequent estimates of radiative lifetimes and corresponding vibronic branching ratios elucidate a dominant contribution of the (4) 1Σ → A ～ b channel into the total radiative decay of the (4) 1Σ state. The relative intensity distributions simulated for (4) 1Σ → X 1Σ+ LIF progressions agree well with their observed counterparts even for the profoundly shifted levels of the entirely perturbed (4) 1Σ state. To get insight into the origin of the intramolecular perturbations, the relevant spin-orbit- and L-uncoupling electronic matrix elements are evaluated.
关键词： electronic structure calculations,Fourier-transform spectroscopy,RbCs molecule,perturbed state,direct potential fit,laser-induced fluorescence,radiative properties
更新于2025-09-23 15:23:52
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Two Dimensional Distribution of Metallic (Cu) Vapor in a Forced Vacuum Arc Extinction by LIF
摘要： It is important to observe the metallic vapor dissipation after interrupting a vacuum arc, for getting a deeper understanding of dielectric recovery processes, especially for DC interruptions. The object of this paper is to obtain two dimensional density distribution of copper vapor in a forced vacuum arc extinction. The method of laser-induced fluorescence (LIF) using a pulse laser with a central wavelength at 324.8 nm was adopted here. Meanwhile, an ICCD was used to capture the 510.6 nm fluorescence signal with an exposure time of 50 ns. The fluorescence can be distinguished from 125 μs (the moment of arc extinction) to 375 μs with a time interval of 25 μs. As a result, we could obtain the relative density distribution of ground-state copper metal vapor after the arc extinction. The results show that on the condition of CuCr25 contacts the metal vapor was evenly distributed in the gap and rapidly spread over time. The density of the copper vapor between the contacts dropped to less than 10% of the initial stage 200 μs after arc extinction. On the contrary, on the condition of CuCr50, higher copper metal vapor density at the moment of arc extinction was observed. It seems that the higher Cr content in the Cu-Cr contacts will lead to producing more metal vapor around current zero.
关键词： laser-induced fluorescence,copper metal vapor,vacuum arc
更新于2025-09-23 15:22:29
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Evaluation of nitric oxide laser-induced fluorescence thermometry techniques in a hypersonic boundary layer
摘要： Nitric oxide planar laser-induced fluorescence was performed to measure the wall-normal distribution of static temperature through a hypersonic boundary layer. A 10-degree half-angle wedge model was oriented at a 5-degree angle of attack in the NASA Langley 31-in Mach 10 facility, resulting in a 5-degree flow turning angle and an edge Mach number of 7.6. Nitric oxide was seeded through a spanwise slot into the boundary layer upstream of the imaging region and was excited with a pulsed ultraviolet planar laser sheet. The laser was spectrally scanned across six fluorescence transitions in the (0, 0) band of the A2Σ+–X2Π system. Eighteen thermometry methods were assessed through comparison to predictions of the temperature field from computational fluid dynamics simulations. The effect of spectral resolution and laser linewidth on measurement uncertainty was also investigated. The most accurate technique was spectral peak thermometry, which achieved an accuracy of ± 31.6 K (12.6% error relative to CFD temperature). The spectral peak thermometry technique required a minimum spectral resolution between 0.074 and 0.102 cm?1 to extract meaningful temperature information from the spectra and a maximum laser linewidth of 0.49 cm?1.
关键词： Laser linewidth,Thermometry,Spectral resolution,Planar laser-induced fluorescence,Hypersonic boundary layer,Nitric oxide
更新于2025-09-23 15:21:01
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Development of laser ablation absorption spectroscopy for nuclear fuel materials: plume expansion behavior for refractory metals observed by laser-induced fluorescence imaging spectroscopy
摘要： The dynamic behavior of an ablation plume in low pressure rare gas ambient was investigated with laser-induced fluorescence imaging spectroscopy for three refractory metals, i.e. titanium, zirconium and hafnium. A comparison of the plume expansion behaviors for the species of these elements revealed an atomic weight effect on the plume structure formation. A hemispherical thin layer and cavity structure reported previously for gadolinium were observed also for these elements. It was found that the plume size increases as well as the layer thickness decreases with increasing atomic weight. For ground state atoms of Ti, substantial amount of atoms were observed even at the center of the plume. Also, the persistence of the Ti atomic plume was as long as 300 μs, which was significantly longer than the other species studied. Furthermore, the mass-dependent elemental separation was observed in the ablation plume produced from a multielement sample. These results suggest that the observed plume structure arises from the ion-electron recombination process and the recoil of the ablated species during the multiple collisions with gas atoms.
关键词： LIBS,Laser-induced fluorescence spectroscopy,Laser ablation,Ablation plume structure,Refractory metals
更新于2025-09-23 15:21:01
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Spectroscopic Studies of M??ssbauer, Infrared, and Laser-Induced Luminescence for Classifying Rare-Earth Minerals Enriched in Iron-Rich Deposits
摘要： Rare-earth (RE) phosphates often appear as an accessory phase in igneous or metamorphic rocks; however, these rocks are composed of myriad chemical elements and nuclides that interfere with the qualitative or quantitative analyses of the RE phosphates over a range of concentrations in the absence of a pretreatment. In addition, the limit of each analytical methodology constrains the approach as well as the usefulness of the results in geoscience applications. Here, we report the specific mineral characterization of RE-containing ores from Yen Phu mine, Vietnam, using a range of state-of-the-art spectroscopic techniques in conjunction with microscopy: M?ssbauer spectroscopy, infrared microspectroscopy, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Because the distribution of each element in the deposit differs, such combinatorial works are necessary and could lead to more plausible answers to questions surrounding the point of origin of RE elements. The results of our M?ssbauer spectroscopic analysis indicate that the three ores sampled at different locations all contain magnetite-like, hematite-like, and iron(III) salts other than hematite. In addition, we confirmed the presence of phosphate around the grain boundary in the magnetite-like mineral phase by infrared microspectroscopic analysis. The present analytical findings of trace amounts of europium(III) using TRLFS suggest that the europium ions generate identical luminescence spectra despite being embedded in three different matrices of iron minerals. This demonstration highlights the benefits of combinatorial spectroscopic analyses to gain insights into the effects of the environment of REs on their solid-state chemistry and shows the potential utility of TRLFS as a resource mining tool. Further applications of this approach in the analytical screening of rocks and minerals are feasible.
关键词： energy-dispersive X-ray spectroscopy,spectroscopic techniques,rare-earth phosphates,Yen Phu mine,infrared microspectroscopy,scanning electron microscopy,time-resolved laser-induced fluorescence spectroscopy,M?ssbauer spectroscopy,Vietnam
更新于2025-09-23 15:21:01
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A novel intracellular signal amplification strategy for the quantification of ATP in single cells by microchip electrophoresis with laser induced fluorescence detection
摘要： An intracellular signal amplification strategy was developed for quantification of ATP in single cells by microchip electrophoresis with laser induced fluorescence detection. By using the method proposed, intracellular ATP levels in single Hela, HepG2 and HL-7702 cell were found in the range of 30～150, 30~140, and 19～120 fmol/cell, respectively.
关键词： laser induced fluorescence,ATP,microchip electrophoresis,single-cell analysis,signal amplification
更新于2025-09-23 15:21:01
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Determination of uranium in ores using laser-induced breakdown spectroscopy combined with laser-induced fluorescence
摘要： The plasma emission spectrum of uranium in laser-induced breakdown spectroscopy (LIBS) is weak and susceptible to spectral interference, especially in a complex ore matrix. In this study, laser-induced breakdown spectroscopy combined with laser-induced fluorescence (LIBS-LIF) technology was proposed to enhance the spectral intensity of uranium in ores and eliminate spectral interference. Different combinations of excitation lines and analytical lines of the U element were investigated. In contrast with atomic lines, uranium ion lines are more suitable for determination of uranium. The relative number of U ions in plasma was studied for the best selection of excitation lines and analytical lines. The analytical performance of LIBS-LIF and LIBS for U determination in ores was compared. The results showed that all indicators had been significantly improved by LIBS-LIF. The slope, R2, LoD, RMSECV, ARE, and ARSD values of LIBS-LIF were 1.1 (cid:1) 105 counts per wt%, 0.998, 35 mg g(cid:3)1, 0.05 wt%, 6.69%, and 6.37%, respectively. This work demonstrates that LIBS-LIF has excellent potential in the exploration of uranium resources.
关键词： laser-induced breakdown spectroscopy,uranium,spectral interference,laser-induced fluorescence,ore matrix
更新于2025-09-23 15:19:57
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Hyperfine structures and isotopic shifts of uranium transitions using tunable laser spectroscopy of laser ablation plumes
摘要： We report isotopic shifts and hyperfine structures of selected U transitions employing tunable spectroscopy viz: laser-induced fluorescence and laser absorption spectroscopy of laser ablation plumes. The plasmas were produced during ns laser ablation on a natural U metal target which contains 0.73% 235U. Our results show that isotopic shifts between 238U and 235U are entangled with hyperfine structures of 235U. Measurements obtained using laser-induced fluorescence are affected by the high absorbance of 238U. Time-resolved laser absorption spectroscopy is carried out for evaluating the optical absorption and estimating the hyperfine constants.
关键词： LIBS,Hyperfine structure,Laser absorption spectroscopy,Isotopic analysis,Uranium,Laser-induced fluorescence,Laser ablation,Tunable laser spectroscopy
更新于2025-09-23 15:19:57
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Rapid analysis of marble treatments by laser induced fluorescence
摘要： Nowadays scientific study of Cultural Heritage accompanies most of the time historical artistic evaluation and an assessment of the conservation state by humanistic experts and restorers. Several laboratory methods with high sensitivity are well established (ICP-MS, FTIR,…), and many methods for in situ rough characterization of large surface are widely diffused (thermovision, UV photography,…), in addition to instrumentation for punctual analysis to be applied also in field (XRF, colorimetry,…). However, the request for systems that can provide rapid detailed characterization on large surface in any storage conditions is still a hot topic. This is combined with the ever-increasing demand for digital material for documentation, fruition and study. Laser-based systems, and in particular Laser Induced Fluorescence (LIF), Laser Induced Breakdown Spectroscopy and Raman spectroscopy, due to the characteristics of these sources and the detectors to which they can be coupled, respond well to these needs. The TECFIS-DIM (Diagnostic and Metrology) Laboratory of the ENEA center of Frascati (Rome, Italy) in the last decade has put an effort to develop more and more compact and efficient laser systems for in situ material characterization on cultural heritage surfaces. Here two prototypal LIF systems have been used to characterize marble surfaces treated with ancient and modern materials and a rapid recognition and mapping method has been developed and tested thanks to the individuation of discriminant spectral features. Results are reported on test samples created in lab with known substances and in situ on real artworks.
关键词： Patinas,Marble,Polymers,Laser spectroscopies,Laser induced fluorescence (LIF)
更新于2025-09-23 15:19:57
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Analysis of combustion instability of hydrogen fueled scramjet combustor on high-speed OH-PLIF measurements and dynamic mode decomposition
摘要： This paper investigated the combustion instability of spanwise positions in a hydrogen fueled scramjet combustor with a cavity flame holder. High-speed OH-PLIF technique was performed on a direct-connect supersonic combustion facility, and dynamic mode decomposition (DMD) as postprocessing. Combustion instability was investigated by characterizing the dominant frequencies and growth factors. By changing the equivalence ratio of hydrogen, the peak frequencies of scramjet mode and ramjet mode were obtained. Scramjet mode tended to have small oscillation at 150e200 Hz reflected by negative growth factors due to the stable flame structure. At ram-to-scram transition, oscillations at 80 e120 Hz were remarkably enhanced due to the positive growth factors. In ramjet mode, the large differences of frequency characteristics in spanwise positions were observed. The dominant DMD modes near the cavity wall appeared to have negative growth factors leading to a stable flame with small oscillations. Besides, the characteristics of frequency-shift were affected by the positions of injector.
关键词： Combustion instability,Dynamic mode decomposition,Dominant frequency,High-speed planar laser-induced fluorescence of OH radicals,Supersonic combustion
更新于2025-09-23 15:19:57