排序方式: 共有72条查询结果,搜索用时 15 毫秒
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Kokh DB Buenker RJ Liebermann HP Pichl L Whitten JL 《The journal of physical chemistry. B》2005,109(38):18070-18080
Configuration interaction calculations of the ground and excited states of the H2CO molecule adsorbed on the Ag(111) surface have been carried out to study the photoinduced dissociation process leading to polymerization of formaldehyde. The metal-adsorbate system has been described by the embedded cluster and multireference configuration interaction methods. The pi electron-attachment H2CO- and n-pi* internally excited H2CO* states have been considered as possible intermediates. The calculations have shown that H2CO* is only very weakly bound on Ag(111), and thus that the dissociation of adsorbed formaldehyde due to internal excitation is unlikely. By contrast, the H2CO- anion is strongly bound to Ag(111) and gains additional vibrational energy along the C-O stretch coordinate via Franck-Condon excitation from the neutral molecule. Computed energy variations of adsorbed H2CO and H2CO- at different key geometries along the pathway for C-O bond cleavage make evident, however, that complete dissociation is very difficult to attain on the potential energy surface of either of these states. Instead, reneutralization of the vibrationally excited anion by electron transfer back to the substrate is the most promising means of breaking the C-O bond, with subsequent formation of the coadsorbed O and CH2 fragments. Furthermore, it has been demonstrated that the most stable state for both dissociation fragments on Ag(111) is a closed-shell singlet, with binding energies relative to the gas-phase products of approximately 3.2 and approximately 1.3 eV for O and CH2, respectively. Further details of the reaction mechanism for the photoinduced C-O bond cleavage of H2CO on the Ag(111) surface are also given. 相似文献
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T. N. Svetlyakova N. G. Kononova A. E. Kokh K. A. Kokh N. A. Pal’chik 《Russian Journal of Inorganic Chemistry》2011,56(1):113-117
Phase formation in the BaB2O4-NaBO2-MBO3 (M = Sc, La, Y) system was studied using solid-phase synthesis, visual polythermal analysis, and spontaneous crystallization. This system was shown to be suitable for growing LaBO3. A new compound, ScBaNa(BO3)2, was obtained (trigonal crystal system; space group R \(\bar 3\) unit cell parameters: a = 5.239(1) Å, c = 34.591(1) Å, and V = 822.38(4) Å3). 相似文献
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V. A. Drebushchak Yu V. Seryotkin Svetlana N. Kokh Ella V. Sokol 《Journal of Thermal Analysis and Calorimetry》2013,114(2):777-783
Three natural minerals of ettringite group were investigated by TG to refine their chemical composition. Two samples are ettringite Ca5.97Mg0.01Sr0.02Al1.99Cr0.01(SO4)3(OH)12·23.7H2O and bentorite Ca5.99Mg0.01Cr1.95Al0.01Si0.03(SO4)2.82·(CO3)0.20(OH)12·19.4H2O, but the third one Ca5.99Na0.01Al1.38Si0.62(SO4)2.49·(CrO4)0.36·(CO3)0.46(OH)12·15.8H2O has found to be a solid solution among ettringite, thaumasite, and chromate-ettringite, not registered yet as a new mineral species. Similar phase is well known in concrete formed with Cr6+ admixture, but is found for the first time as a natural compound. X-ray single-crystal investigation allowed us to refine the structure and support substitution (SO4)2? ? (CrO4)2? in natural minerals of ettringite group. 相似文献
4.
Yu. S. Ponosov T. V. Kuznetsova O. E. Tereshchenko K. A. Kokh E. V. Chulkov 《JETP Letters》2014,98(9):557-561
Raman measurements of the phonon spectrum of BiTeI at pressures of up to 20 GPa have been performed. A decrease in the linewidth of E2 vibration by almost a factor of 2 with an increase in the pressure to 3 GPa has been detected. The frequencies of all four Raman active modes increase monotonically with the pressure. These lines are observed in spectra up to ~8 GPa. Sharp change in the spectrum occurs at pressures of 8–9 GPa, indicating a transition to the high-pressure phase, which holds up to 20 GPa. This transition is reversible and hardly has any hysteresis. A sample in the high-pressure phase is single crystal. 相似文献
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A. Kokh E. Simonova A. Maillard R. Maillard V. Svetlichnyi Yu. Andreev A. Kragzhda A. Kuznetsov K. Kokh 《Crystal Research and Technology》2016,51(9):530-533
The bulk crystals of LiBa12(BO3)7F4 were obtained from two flux compositions by the top seeded solution growth method. Crystals grown from BaCO3:BaF2:H3BO3:Li2CO3 = 3:3:3:1 charge were found to have a distinct linear dichroism effect at 0.35–0.65 and around 0.73 μm. This suggests application of the material in the production of polarizing filters and attenuators for visible range lasers. 相似文献
7.
T. B. Bekker N. G. Kononova A. E. Kokh S. V. Kuznetsov P. P. Fedorov 《Crystallography Reports》2010,55(5):877-881
The phase equilibria in the Ba2Na3[B3O6]2F-BaF2 section, which belongs to the ternary mutual Ba, Na//BO2,F system, have been studied by the methods of solid-phase synthesis, visual polythermal analysis, and differential-thermal
analyses. It is shown that this section can be used to grow bulk Ba2Na3[B3O6]2F crystals. 相似文献
8.
Ying-Fei Zhang Zhi-Hui Kang Yun Jiang Yury M. Andreev Konstantin A. Kokh Anna V. Shaiduko 《Optics Communications》2011,284(6):1677-1681
We report a systematic study of AgGaS2- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS2-doped GaSe (GaSe:AgGaS2) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS2 (10.6 wt.%). Its real composition was identified as GaSe:S (2 wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass % of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2 wt.%) crystal grown from the melt of GaSe:AgGaS2 is 25% higher than that of GaSe:S (2 wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤ 10− 7 Om− 1 cm− 1. A comparative experiment on SHG in AgGaS2-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12-2.9 μm fs OPA and 9.2−10.8 μm ns CO2 laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application. 相似文献
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Potential energy curves for the X (1)Sigma(g) (+) ground state and Omega=0(u) (+), 1(u) valence states and dipole moments for the 0(u) (+), 1(u)-X transitions are obtained in an ab initio configuration interaction study of Cl(2) including spin-orbit coupling. In contrast to common assumptions, it is found that the B (3)Pi(0(+)u)-X transition moment strongly depends on internuclear distance, which has an important influence on the Cl(2) photodissociation. Computed energy curves and transition moments are employed to calculate the A, B, C<--X extinction coefficients, the total spectrum for the first absorption band, and the Cl(*)((2)P(1/2))/Cl((2)P(3/2)) branching ratio as a function of excitation wavelength. The calculated data are shown to be in good agreement with available experimental results. 相似文献