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Photon catalysis of deuterium iodide photodissociation
摘要： A catalyst enhances a reaction pathway without itself being consumed or changed. Recently, there has been growing interest in the concept of "photon catalysis" in which nonresonant photons, which are neither absorbed nor scattered, promote reactions. The driving force behind this effect is the interaction between the strong electric field associated with a pulsed, focused laser and the polarizability of the reacting system. In this study, the effect of near-infrared, nonresonant radiation on the photodissociation of deuterium iodide is demonstrated. We use nanosecond pulses rather than time-resolved spectroscopy to investigate the average effect of the electric field on the branching ratio for forming D + I(2P3/2) and D + I(2P1/2). Changes in the measured D-atom speeds between field-free and strong-field conditions confirm substantial differences in dissociation dynamics. Both the magnitude and direction of change in the branching ratios are dependent upon the photodissociation wavelength. Experiments and theoretical calculations confirm that the mechanism for photon catalysis under these conditions is dynamic Stark shifting of potential energy surfaces rather than electric-field-induced alignment of reagent molecules.
关键词： deuterium iodide,dynamic Stark shifting,photon catalysis,photodissociation,nonresonant radiation,branching ratio
更新于2025-09-19 17:15:36
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Effect of Ar(3p <sup>5</sup> 4p; 2p)+M → Ar(3p <sup>5</sup> 4s; 1s)+M branching ratio on optically pumped rare gas laser performance
摘要： Optically pumped rare gas laser performance is analyzed as a function of the Ar(3p54p; 2p) + M → Ar(3p54s; 1s) + M branching ratios. Due to the uncertainty in the branching ratios, a sensitivity study is performed to determine the effect on output and absorbed pump laser intensities. The analysis is performed using a radio frequency dielectric barrier discharge as the source of metastable production for a variety of Argon in Helium mixtures over pressures ranging from 200 to 500 Torr. Peak output laser intensities show a factor of 7 increase as the branching ratio is increased from 0.25 to 1.00. The collection of Ar* in Ar(1s4) is inversely proportional to the branching ratio and decreases output laser intensity by reducing the density of species directly involved with lasing.
关键词： Argon,Helium,branching ratio,radio frequency dielectric barrier discharge,metastable production,optically pumped rare gas laser
更新于2025-09-16 10:30:52
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Luminescence properties of Nd3+ ions doped P2O5-Li2O3-GdF3 glasses for laser applications
摘要： The phosphate glass doped with Nd3+ ions, is a recognized high gain laser material due to better spectroscopic properties. In present study, the luminescent properties of Nd3+ doped lithium-gadolinium phosphate glasses were investigated. The compactness of the glass matrix believed to increase with increasing concentration of Nd2O3 contents, because the density of the samples also increases in same fashion. Furthermore, the emission spectra monitor after 804 nm excitation show three emission peaks at 874, 1065 and 1333 nm. In the present work maximum emission intensity recorded for 1 mol% of Nd2O3 and above 1 mol% the emission intensity decrease. The Judd-Ofelt (JO) theory applied to calculate the JO intensity parameters (Ω2, 4, 6), oscillator strength for absorption spectra, several radiative properties for the prepared glasses. The calculated JO intensity parameters show the Ω4 > Ω6 > Ω2 trend which indicate rigid nature of the present glasses. The radiative transition probability, stimulated emission cross section and branching ratio show higher values for 4F3/2→4I11/2 transition. From properties evaluated in the present work it is concluded that the glass doped with 1.0 mol% Nd2O3 can be a potential candidate for laser applications.
关键词： Oscillator strengths,Branching ratio,Luminescent properties,JO theory
更新于2025-09-16 10:30:52
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Fingerprinting electronic structure of heme iron by ab initio modeling of metal L-edge X-ray absorption spectra
摘要： The capability of the multiconfigurational restricted active space approach to identify electronic structure from spectral fingerprints is explored by applying it to iron L-edge X-ray absorption spectroscopy (XAS) of three heme systems that represent the limiting descriptions of iron in the Fe-O2 bond, ferrous and ferric [Fe(P)(ImH)2]0/1+ (P = porphine,ImH = imidazole), and FeII(P). The level of agreement between experimental and simulated spectral shapes is calculated using the cosine similarity, which gives a quantitative and unbiased assignment. Further dimensions in fingerprinting are obtained from the L-edge branching ratio, the integrated absorption intensity, and the edge position. The results show how accurate ab initio simulations of metal L-edge XAS can complement calculations of relative energies to identify unknown species in chemical reactions.
关键词： multiconfigurational restricted active space,branching ratio,integrated absorption intensity,iron L-edge X-ray absorption spectroscopy,electronic structure,cosine similarity,edge position,heme systems,spectral fingerprints
更新于2025-09-10 09:29:36