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Explicit expressions for the Green functions of arbitrary relativistic quadratic quantum systems are obtained by the integrals-of-motion method and by the coherent states method. The normal forms of the relativistic quadratic hamiltonians are briefly discussed. The important special cases, such as the motion of Dirac and Klein-Gordon charged particles in the fields of a plane wave and in the uniform electric and magnetic fields are investigated in detail. 相似文献
244.
A method is presented for analyzing, in terms of sum rules, the intensity distribution among the vibronic bands in electronic spectra of polyatomic molecules, taking into account the rotation of the excited-state normal coordinates relative to those of the ground state (the Dushinsky effect). In the harmonic oscillator approximation, a quantitative criterion for the occurrence of the Dushinsky effect is obtained. The existence of this effect leads to non-product formulas for probabilities of the joint excitation of different vibrational modes. Expressions are obtained for the mean number of quanta excited in a given mode, and for its standard deviation, as well as for the correlation coefficients. The proposed method does not require a complete vibrational analysis of the spectrum of interest. As an example, the calculation of the correlation coefficient for the 3700-Å band system of the absorption spectrum of SO2 is given. 相似文献
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Conclusions The extinction coefficients of the short-lived colored form of some spiropyrans of the phenanthridine series were determined for the first time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 643–644, March, 1979. 相似文献
248.
In terms of a semiphenomenological exchange charge model, we have obtained estimates of parameters of the crystal field and parameters of the electron-deformation interaction in terbium titanate Tb2Ti2O7 with a pyrochlore structure. The obtained set of parameters has been refined based on the analysis of spectra of neutron inelastic scattering and Raman light scattering, field dependences of the forced magnetostriction, and temperature dependences of elastic constants. 相似文献
249.
B. Z. Malkin M. V. Vanyunin M. J. Graf J. Lago F. Borsa A. Lascialfari A. M. Tkachuk B. Barbara 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):155-163
Temperature and magnetic field dependences of the 19F
nuclear spin-lattice relaxation in a single crystal of LiYF4 doped
with holmium are described by an approach based on a detailed consideration
of the magnetic dipole-dipole interactions between nuclei and impurity
paramagnetic ions and nuclear spin diffusion processes. The observed
non-exponential long time recovery of the nuclear magnetization after
saturation at intermediate temperatures is in agreement with predictions of
the spin-diffusion theory in a case of the diffusion limited relaxation. At
avoided level crossings in the spectrum of electron-nuclear states of Ho3
+ ions, rates of nuclear spin-lattice relaxation increase due to
quasi-resonant energy exchange between nuclei and paramagnetic ions in
contrast to the predominant role played by electronic cross-relaxation
processes in the low-frequency ac-susceptibility. 相似文献
250.
Prof. Dr. Sc. A.Ya. Malkin S.A. Bolgov V.P. Begishev V.A. Mansurov 《Rheologica Acta》1992,31(4):345-350
Simultaneous measurements of the components of dynamic modulus at the set of frequencies were made by Fourier-Transform Mechanical Spectroscopy (FTMS) to investigate the curing process of a segmented polyurethane.The whole process of curing is treated as consisting of three stages. In the first stage, the material can flow and this stage is complete at the gel-point. In the second stage, the curing proceeds in the network and ends with phase separation of aggregating segments (blocks) of polymeric chains. In the third stage, the curing continues in the two-phase system. The object of investigation was the transition from the second to the third stage. It was shown that the position of the maximum of loss tangent depends on frequency and does not coincide with different characteristic points marking the time dependencies of G and G. This is due to the formation of micro-particles of the newly formed phase. The FTMS method is used for separation of the modulus changes into parts related to formation of chemical and physical networks.Special means of treating calorimetric measurements identified a weak maximum heat output at the moment corresponding to the transition point. 相似文献