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51.
The X-band ( x ; 9.4 v GHz) electron spin resonance (ESR) spectra of the un-doped isotopically enriched lithium tetraborate (LTB) Li 2 B 4 O 7 single crystals, irradiated by thermal neutrons (fluences | n =2.74 ‐ 10 15 1 1.79 v ‐ 10 18 v cm m 2 ) were investigated at 300 and 77 v K. The LTB crystals of high chemical purity and optical quality with different isotope compositions ( 6 Li 2 10 B 4 O 7 , 6 Li 2 11 B 4 O 7 , 7 Li 2 10 B 4 O 7 and 7 Li 2 11 B 4 O 7 ) were grown by Czochralski technique. The thermal neutrons (the total quantity >90%) with fluence near 10 18 v cm m 2 induce at least 4 different types of stable paramagnetic centers in the Li and B isotopically enriched LTB crystals. The ESR spectra, electron structure and efficiency of generation for centers, induced by thermal neutrons, essentially depend on neutron fluence and isotope composition of the LTB crystals. The local symmetry and the spin Hamiltonian parameters of the observed paramagnetic centers were determined and their electron structure were established. The possible models and formation mechanism of the radiation defects, induced by thermal neutrons in the LTB lattice, are proposed. 相似文献
52.
Statistical distributions of the frequencies of OH vibrations calculated from the experimental Raman spectra of HOD molecules over the temperature range of 10–200 C using the recently developed deconvolution technique have been analysed in the framework of fluctuation theory of hydrogen bonding. Two temperature independent functions that are the basis of the Zhukovsky theory for describing the temperature transformation of frequency distribution functions of OH vibrations in a statistical ensemble of O—H…O bonds were established and analytically approximated. This made it possible to reconstruct the entire set of initial spectra and to extrapolate their forms to a wider temperature range. These results support the continuum model of liquid water structure. 相似文献
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N. YA. Turova E. P. Turevskaya V. G. Kessler M. I. Yanovskaya 《Journal of Sol-Gel Science and Technology》1994,2(1-3):17-23
X-ray structural analysis of crystalline alkoxides in many cases reveals that along with OR-groups their molecules also contain oxo-ligands. The following possible reactions leading to formation of oxoalkoxides have been discussed: hydrolysis, pyrolysis (frequently uncontrollable), ether elimination, oxidation of OR-groups (which exist in solutions of alkali, alkaline-earth and rare earth elements), or alkoxides of the lower oxidation states (which are formed by reduction of M(OR)
n
on cathode during electrolysis or by hydrogen in statu nascendi). Oligomeric oxoalkoxides differ from the polymeric alkoxides M(OR)
n
in considerably higher solubility and reactivity. The most important role of oxoalkoxides in the processes of formation of oxides has been demonstrated using as an example preparation of BaTiO3 from alkoxides. 相似文献
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Tosin M Demydchuk Y Parascandolo JS Per CB Leeper FJ Leadlay PF 《Chemical communications (Cambridge, England)》2011,47(12):3460-3462
Early-stage intermediates in the biosynthesis of erythromycin A by Saccharopolyspora erythraea were intercepted by malonyl carba(dethia)-N-acetyl cysteamines, generated in vivo from the hydrolysis of the corresponding methyl esters. 相似文献
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The reaction of anhydrous YbCl3 with 1 equiv, of Li2Me2Si(NPh)2 in THF, after workup, yielded a ytterbium(Ⅲ) chloride [{Me2Si(NPh)2Yb}(μ2-CI)(TMEDA)]2·3PhMe (1) (TMEDA=tetramethylethanediamine). The same reaction followed by treatment with Na-K alloy afforded a new ytterbium(H) complex supported by a bridged diamide with four coordinated LiC1 molecules, [{Me2Si(NPh)2Yb(THF)2}(μ3-CI)(μ4-CI){Li(THF)}2]2·2THF (2) in high yield. Both complexes were structurally characterized by X-ray analysis to be dimers. Complex 1 was a chlorine-bridged dimer with ytterbium in a distorted octahedral geometry. In complex 2 two [Me2Si(NPh)2Yb(THF)2]- (μ3-CI)[Li(THF)]2 moieties were connected with each other by two μ4-CI bridges to form a "chair-form" framework. 相似文献