Transfer and Trapping of Resonance Radiation in a Two-Level System

Optics and Spectroscopy - The population kinetics of a two-level system has been theoretically investigated taking into account the transfer of spontaneous radiation under continuous optical...     

Deposition of amorphous hydrogenated semiconductors by magnetron assisted silane decomposition

Magnetron assisted silane decomposition (MASD) is proposed as a method for deposition of a-Si:H and its alloys. In this method a silane containing gas mixture is passed through the magnetron plasma near a target and decomposed there. The deposition rate in the case of the c-Si target is increased 3 times compared to magnetron sputtering and film properties are changed. a-SiSn:H is obtained with a Sn target.     

Exciton molecules and exciton liquids in semiconductors

Excitons in many-valley semiconductors form molecules consisting of four and more excitons. The degeneracy factor g of the conduction band in germanium is 8, and in silicon g=12. As in acceptors, the hole ground state in excitons is fourfold degenerate. The same is valid for exciton molecules, because they are quantum objects with spherical symmetry. The exciton binding energy in molecules is close to that in exciton-liquid droplets. Experimental evidence is considered for the existence, besides biexcitons, of stable exciton molecules consisting of three and four, and, possibly, 11 and 12 excitons. Molecules containing from five to ten excitons are apparently unstable. Fiz. Tverd. Tela (St. Petersburg) 40, 929–931 (May 1998)     

Structure and energy studies of β-diketonates. XIII. Molecular structure of gadolinium tris-hexafluoroacetylacetonate Gd(C5O2HF6)3

In a mass spectrometric study, it was found that the saturated vapor over gadolinium tris-hexafluoroacetylacetonate Gd(C₅O₂HF₆)₃ contains molecular forms with a mass exceeding the mass of the dimer. The vapor overheated to 250–300°C contains only the monomer form. Simultaneous electron diffraction and mass spectrometric experiment aimed at investigating the structure of the Gd(hfa)₃ monomer molecule was carried out at 284(5)°C. The Gd(hfa)₃ molecule was found to have the symmetry of the equilibrium D ₃ configuration. The basic structural parameters are r _h1(Gd-O) = 2.291(10) Å, r _h1(O-C) = 1.257(10) Å, r _h1(C-C_r) = 1.404(6) Å, r _h1(C_F-F)_av = 1.341(3) Å, ∠OGdO = 72.8(0.4)°. The GdO₆ coordination polyhedron has the structure of a distorted antiprism. The rotation angle of the O-O-O trigonal faces relative to their position in a regular prism is 18.7(0.9)°. Quantum chemical calculations (HF/SBK, 6-31G*) generally reproduce the experimental structure, but the Gd-O internuclear distance is exaggerated by 0.04 Å.     

Reaction of 2,6-dibenzylidenecyclohexanone with phosphorus pentachloride: Triple functionalization of the isosemiquinoid system

The reaction of 2,6-dibenzylidenecyclohexanone with PCl₅ occursvia the sequential stages of desoxychlorination and substitutional phosphorylation to form (after oxidation, methoxylation, and hydrolysis on the surface of the chromatographic SiO₂ adsorbent) organophosphorus products of the 1-(a-chloro-, a-hydroxy-, or -alkoxy)benzyl-2-chloro-3-(-(dimethylphosphoryl)benzylidene)cyclobex-1-ene series.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 441–443, February, 1996.     

Molecular ions of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides

The electrochemical reduction of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides (R = CF₃, Me, Ph, Bu^t), which are cyclic dinitrons with conjugated C=C bond, in acetonitrile is an EE process producing stable radical anions and dianions, whereas the electrochemical oxidation is an EEC (R = Me, Ph) or EE process (R = Bu^t) with formation of radical cations (except for the case of R = CF₃) and dications (R = Bu^t) stable under standard conditions. Radical cations of the dioxides with R = Me, Ph, and Bu^t and radical anions of the whole series of the compounds studied, including R = CF₃, were characterized by ESR spectroscopy combined with electrochemical measurements and quantum-chemical calculations. The electrochemical behavior of the Bu^t-substituted dinitron is unique: the EE processes in the region of negative and positive potentials with formation of the dianion, radical anion, radical cation, and dication stable at T = 298 K were observed for the first time within one cycle of potential sweep in the CV curve measured in MeCN. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1148–1154, May, 2005.