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Alperovich I Smolentsev G Moonshiram D Jurss JW Concepcion JJ Meyer TJ Soldatov A Pushkar Y 《Journal of the American Chemical Society》2011,133(39):15786-15794
L(2,3)-edge X-ray absorption spectroscopy (XAS) has demonstrated unique capabilities for the analysis of the electronic structure of di-Ru complexes such as the blue dimer cis,cis-[Ru(III)(2)O(H(2)O)(2)(bpy)(4)](4+) water oxidation catalyst. Spectra of the blue dimer and the monomeric [Ru(NH(3))(6)](3+) model complex show considerably different splitting of the Ru L(2,3) absorption edge, which reflects changes in the relative energies of the Ru 4d orbitals caused by hybridization with a bridging ligand and spin-orbit coupling effects. To aid the interpretation of spectroscopic data, we developed a new approach, which computes L(2,3)-edges XAS spectra as dipole transitions between molecular spinors of 4d transition metal complexes. This allows for careful inclusion of the spin-orbit coupling effects and the hybridization of the Ru 4d and ligand orbitals. The obtained theoretical Ru L(2,3)-edge spectra are in close agreement with experiment. Critically, existing single-electron methods (FEFF, FDMNES) broadly used to simulate XAS could not reproduce the experimental Ru L-edge spectra for the [Ru(NH(3))(6)](3+) model complex nor for the blue dimer, while charge transfer multiplet (CTM) calculations were not applicable due to the complexity and low symmetry of the blue dimer water oxidation catalyst. We demonstrated that L-edge spectroscopy is informative for analysis of bridging metal complexes. The developed computational approach enhances L-edge spectroscopy as a tool for analysis of the electronic structures of complexes, materials, catalysts, and reactive intermediates with 4d transition metals. 相似文献
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M. R. DE BACKER-BARILLY A. BARBE S. A. TASHKUN VL. G. TYUTEREV A. CHICHERY 《Molecular physics》2013,111(22):3499-3506
The four 5v 3 bands of 18O enriched ozone have been observed and analysed for the first time. Two species (16O18O16O and 18O16O18O) belong to the C2v symmetry group and two other (18O18O16O and 16O16O18O) to the Cs symmetry group. They have been recorded at a resolution of 0.008 cm?1 with a pathlength of 32.16 m. Despite the very weak absorptions observed, almost 250 energy levels have been derived for each of the 4 species, with J ? 35 and K a ? 13, and suitable sets of Hamiltonian parameters have been determined. For 3 species it has been necessary to account for the resonance between the (005) and (311) states to correctly reproduce the spectra observed. These resonances, anharmonic for C2v, and hybrid (both anhar-monic and Coriolis) for Cs symmetry confirm the accidentally extremely strong coupling between the (005) and (311) states for 16O3, due in that case to the very close distance between unperturbed energy levels. This work also confirms the excellent prediction of band centres of these four species derived from the recently determined isotopically invariant molecular potential function. 相似文献
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It has been found experimentally that the probability of emitting electrons from p-GaAs(Cs,O) to vacuum in the presence of a magnetic field depends on the sign of the circular polarization of exciting light. The main cause of this effect is the jump in the electron g-factor at the semiconductor-vacuum interface (from g* = ?0.44 in GaAs to g 0 = 2 in vacuum). Owing to the jump in the electron g-factor, the effective electron affinity depends on the mutual orientation of optically oriented electrons and the magnetic field and this dependence results in the spin-dependent photoemission. 相似文献
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It has been found experimentally that the bond energy of arsenic atoms on the GaAs(100) surface decreases under the influence of adsorbed cesium. This is manifested in the disordering of the As-stabilized surface and in a decrease of ~(100 K in the temperature of the transition to the Ga-stabilized (100)GaAs(4×2)/c(8×2) surface. This effect is caused by the redistribution of the valence electron density between the arsenic atoms in the upper layer and the gallium atoms in the lower-lying layer as a result of charge transfer from the electropositive adsorbate to the semiconductor. In combination with the analogous effect of a decrease in the bonding energy of gallium atoms on the Ga-stabilized GaAs surface upon the adsorption of electronegative adsorbates (halogens), the effect observed allows the atomic layer etching of the polar GaAs(100) face. 相似文献
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JETP Letters - A nonmonotonic behavior of band bending φ S as a function of cesium coverage ? on the Cs/GaAs(001) surface is observed in the form of several maxima and minima. This... 相似文献
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S.N. Mikhailenko VL.G. TyuterevV.I. Starikov K.K. AlbertB.P. Winnewisser M. Winnewisser G. MellauC. Camy-Peyret R. LanquetinJ.-M. Flaud J.W. Brault 《Journal of Molecular Spectroscopy》2002,213(2):91-121
Water vapor infrared spectra have been recorded at room temperature in the range 4200-6250 cm−1 at resolutions (FWHM) between 0.0053 and 0.0080 cm−1. The use of a White-type multireflection cell made large pressure × pathlength products possible up to 31.27 mbar×288.5 m. The high signal-to-noise ratio allowed us to observe lines with intensities as small as 10−26 cm−1/molecule cm−2 at T=296 K. Among about 5100 recorded water lines, about half of which are reported for the first time, 2351 lines have been assigned to the second triad of H216O (bands ν1+ν2, ν2+ν3, and 3ν2). This has allowed the determination of line positions and corresponding upper rovibrational states with considerably improved accuracy. The assignments of certain highly excited states have been confirmed by the analysis of flame spectra and hot emission spectra. New values of effective Hamiltonian parameters for the upper states {(110), (030), (011)} have been determined. The generating function model was used in the data reduction to account for the anomalously strong centrifugal distortion of the rovibrational levels and resonance interactions. The RMS standard deviation of the least-squares fit of the assigned H2O data was 5×10−3 cm−1 for line positions and 7×10−3 cm−1 for energy levels up to Jmax=20 and Ka(max)=13. Particular attention was paid to water lines in the transparency window 4200-5000 cm−1, in which existing databases are not sufficient. In this region, 1395 lines of four isotopic species of water have been recorded and over 900 accurate line positions of nine bands of H216O (ν1, ν3, 2ν2, ν1+ν2, ν2+ν3, 3ν2, 4ν2−ν2, 2ν2+ν3−ν2, ν1+2ν2−ν2) are reported in this range. A comparison of laboratory spectra with long path atmospheric spectra (20 km slant path in the mountains) in this region shows that many lines missing from available spectroscopic compilations (or considerably shifted compared to observations) are important for a proper interpretation of atmospheric observations. A comparison of the observed data with the best available predictions from the molecular electronic potential energy surface is discussed. 相似文献
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Stability radii for some propagation models 总被引:2,自引:0,他引:2
The simple idea of Hinrichsen & Pritchard who defined thestructured stability radius has proved to be unexpectedly fruitful,generating a large amount of work and making interesting connections.The aim of this paper is twofold: to study stability radii forsome specific propagation models and to make connections withresults on Popov-type frequency-domain stability inequalities. 相似文献
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Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献