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61.
The collisional broadening and shift of four spectral lines of neon (747.2, 748.8, 753.5, 754.4 nm) arising from 2p5 3p - 2p5 3d transitions, emitted from a low-pressure glow discharge in pure neon and neon-helium mixtures have been measured using a Fabry-Perot interferometer. The values of pressure broadening and shift coefficients are determined and analyzed in terms of the impact theory. 相似文献
62.
For a large class of intermolecular potentials, the values of the second virial coefficient at a discrete set of temperature points in an arbitrarily small neighborhood of the origin determine the potential uniquely. 相似文献
63.
在高极化多自旋液体样品中,同时存在着分子间偶极(D)耦合和分子内标量(J)耦合,它们的共同作用产生了一些原来观测不到的分子间多量子相干信号。而且,信号的裂分模式与只存在J耦合的多自旋体系中观测到的多量子相干信号的裂分模式不同。本文从理论和实验上研究了这些禁阻的共振峰及其独特的裂分模式。为了比较验证,我们以I2S3+X自旋体系为例,结合使用选择和非选择性的射频脉冲序列来获得分子间双量子相干信号的五种裂分模式。进而归纳出对IpSq+Xk (p, q, k = 1, 2, 3,…)自旋体系普适的裂分模式规则。并指出,它们中如(1:0:-1)的裂分模式会放大J耦合裂分,使得J耦合常数的测量更精确,特别在J耦合常数很小或不均匀场中的J耦合常数的测量中具有诱人的应用前景。结果表明理论预测,计算机模拟和实验观测结果三者吻合的很好。 相似文献
64.
IR spectra,conformational lability,and intermolecular interactions in long-chain aliphatic compounds
Investigations of the conformational lability and intermolecular interactions in long-chain aliphatic compounds (LACs), namely, in carboxylic acid derivatives (alkyl- and alkoxybenzoic acids; alkylcyclohexanecarboxylic acids and their completely or partially fluoroalkyl-substituted derivatives), 4-cyano-4-p-alkoxybiphenyls, 4-cyano-4-p-alkylbiphenyls, and cholesterol p-n-butyloxybenzoate are reviewed. Major attention is paid to experimental and theoretical IR spectroscopy data. Differential thermal analysis, polarization microscopy, and X-ray diffraction data are also taken into account. A more detailed treatment is presented on IR spectrum simulation based on data about the conformational lability of molecules and their specific (H-bonding) intermolecular interactions. The first mechanism is responsible for the conformational type of polymorphism in LACs and for the structure of the latter in solid crystal (SC) and liquid crystal (LC) states and in isotropic liquids (ILs). The second mechanism complements the structure-forming aspect of polymorphism in carboxylates, which is due to a rearrangement of hydrogen bond systems in H-complexes during polymorphic transitions to the LC and IL states. Both mechanisms are reflected in IR absorption spectra. A more adequate interpretation is possible in order to explain the many spectral features associated with the structure of LAC polymorphs and their H-complexes if these mechanisms are taken into account.Original Russian Text Copyright © 2004 by L.M. BabkovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 389–397, May–June, 2004. 相似文献
65.
Intermolecular photoinduced electron transfer (PET) in a gas phase was studied using carbazole vapor fluorescence quenching by halomethanes (CHCl3, CH2Br2, CCl4, CHBr3). The fluorescence quenching rate constants k
q changing from 2.3·105 sec–1·torr–1 in mixtures with CHCl3 to 4.6·106 sec–1·torr–1 in mixtures with CHBr3 at a constant temperature of 403 K were estimated. The dependence of the carbazole fluorescence decay rates in the presence of halomethanes on the free energy change G during transfer of the electron from carbazole to halomethanes is considered. It is suggested to take into account the influence of the vibrational energy of the carbazole molecule E
vib and its temperature changes in estimation of the G values. The differences between PET in the gas and liquid phases were analyzed. It is found that for mixtures with CCl4 and CHBr3 the negative temperature dependence of k
q is observed, when the decay rates and efficiencies of the intermolecular PET decreased with temperature increase in the range 403–573 K, i.e. these mixtures the electron transfer is not a barrier-restricted process. 相似文献
66.
67.
Summary An approach is described which makes use of X-ray structural data from enzyme-ligand complexes in order to obtain information for application in receptor modelling. The atomic surroundings of five different ligand functional groups were determined for all complex structures recorded in the Brookhaven Protein Data Bank. These atomic surroundings were then superimposed with respect to the atoms of the functional groups of the ligands in order to obtain clouds of neighbouring atoms. General principles were sought to describe the orientiation or favoured position of groups or atoms around those functional groups when bound to a macromolecule. Some simple conclusions and leads for further modelling were thus derived. 相似文献
68.
69.
Günter Haufe Thomas C. RosenOliver G.J. Meyer R. FröhlichKari Rissanen 《Journal of fluorine chemistry》2002,114(2):189-198
Monofluorinated cyclopropanecarboxylates are available in racemic or optically active form by transition metal-catalyzed reactions of vinylfluorides with diazoacetates. From α-fluorostyrene and tert-butyl diazoacetate in the presence of 2 mol% of an enantiopure bis(oxazoline) copper complex, a 81:19 mixture of tert-butyl trans- and cis-2-fluoro-2-phenylcyclopropanecarboxylates was obtained with high enantiomeric excess (ee) of 93 or 89%, respectively. The corresponding racemic ethylesters were used as starting materials for the synthesis of carboxamides, of the cis- and trans-isomers of analogues of tranylcypromine, an anti-depressive drug and several of its homologous fluorinated cyclopropylmethyl and cyclopropylethyl amines. Corresponding enantiopure cyclopropylmethanols and several of their derivatives were synthesized also. Solid state structures of a selection of these compounds were examined by X-ray crystallography. Particularly, the cis-configurated fluorinated phenylcyclopropane derivatives showed extremely close intermolecular CH?FC contacts. The shortest of such distances (2.17 Å) was found in the N-(4-bromophenyl)carbamate of (1S,2R)-(2-fluoro-2-phenylcyclopropyl)methanol. 相似文献
70.
L. I. Belen’kii G. P. Gromova V. I. Smirnov 《Chemistry of Heterocyclic Compounds》2008,44(9):1092-1100
We have studied the possible modification of 2,5-di(thienyl)pyrroles with the aim of preparing compounds which can serve as
precursors of polymers and monomers showing electrical conductivity and specific photochemical properties.
Dedicated to Boris Aleksandrovich Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1356–1365, September, 2008. 相似文献