关键词： Differential Geometry   Planetary Orbit   Shift Calculation   Perihelion Precession   Perihelion Shift  

摘要： In this paper an attempt is made to resolve a confusion which exists in the literature over whether the perihelion precession of planetary orbits is a linear or non-linear effect. The problem is both one of physics and semantics. © 1974 Plenum Publishing Company Limited.

摘要： The Knight shift Ks and nuclear spin-relaxation time T1 have been calculated in liquid Mg using the pseudopotential theory. The results of this calculation show that both Ks and T1T are independent of temperature T within the error in our calculation. The calculated value of Ks at the melting temperature (651 ° C) is (0.10 ± 0.005)% which compares well with the recent experimental measurement (0.112 ± 0.004)% made between - 196 and 230 ° C. From this evidence, it can be concluded that there is no significant change of Ks upon melting, contrary to what has been observed in Cd. The theoretical value of the Korringa ratio, (Ks2T1T)theor(Ks2T1T)ideal, departs from its ideal value of unity by about 17%. This departure is attributed to the different role of exchange enhancement on the uniform and nonuniform spin paramagnetic susceptibilities.

摘要： Calculations of chemical shifts for carbon, nitrogen and oxygen are presented. The method is similar to that proposed by Pople and Santry for N.M.R. coupling constants. Wave functions were calculated from an extended Hückel model without overlap and a restricted set of excited states used to evaluate the paramagnetic term. Using a single parameter for each atom reasonable results were obtained.

摘要： The chemical shift of nuclei in molecules and solids is determined by the interaction of the nuclear magnetic moment with the orbital currents of electrons induced by the applied magnetic field. Exactly soluble systems exist, but in most cases perturbational or variational methods must be employed. Of these, the perturbed Hartree-Fock method yields the best results but is presently limited to small molecules, except in the case of proton shieldings due to pi-electron ring currents. The average energy denominator approximation associated with expansion of the perturbed wave function in a complete set is of particular interest because of its relative simplicity. This approximation is examined in detail and some justification of its use is given. Calculations which have been performed for atoms, diatomic and non-aromatic polyatomic molecules, aromatic molecules, and solids are summarized. Electric field effects are of considerable importance in the chemical shifts of protons. Empirical rules and correlations are briefly discussed. © 1967.

关键词： 矿山   岩层移动   学科:计算  

ISBN: (纸本)15035·850