[en] The recent discovery by Khare that choosing the CS partial wave parameter l-bar to be the initial orbital angular momentum, l/sub i/, leads to a simple differential scattering amplitude for definite polarization transitions is examined in detail. It is found that the resulting scattering amplitude formula, which is a rotation of the usual McGuire--Kouri formula, predicts nonzero magnetic transitions in all frames except that whose Z axis always points in the final observation direction R. A detailed comparison of l/sub i/ and l/sub f/ labeling is made and it is shown that both lead to nondiagonal approximations to the p-helicity amplitude, T/sup J/(jlambdavertical-barj₀m₀), and to differential scattering amplitudes which have the proper limiting behavior at small and large scattering angles. In addition it is shown that both l/sub i/ and l/sub f/ labeling yield identical results for all degeneracy averaged cross sections, including the general relaxation cross sections. Further, we show rigorously that if the quantization axis is along a direction perpendicular to the plane of the incident and final momenta, then the l/sub i/ and l/sub f/ labeled cross sections are identical. It is argued on the basis of available numerical results and on physical grounds that the l/sub i/-labeled CS is preferred over the l/sub f/ CS for calculating magnetic transitions quantized along the incident momentum. We further expect the l/sub f/ CS to be preferred for calculating magnetic transitions quantized along the final momentum. However, other l-bar choices may be better yet for magnetic transitions in general

[en] The dipole moment appearing in a pair of polyatomic molecules during a collision, originating from the dynamic correlation of the charges between the two systems, is formulated using two different methods. The first one introduces the electro-optical effect induced in one of the partners by the fluctuating field of the other and by an externally applied field. The second method takes into account the optical rectification processes of one molecule subjected to the fluctuating field of the other. These formalisms may be applied to pairs with any molecular symmetry. An application is made to molecules belonging to the T/sub d/ group, showing that in such a case the R^-₇ part of the dispersion polarization may be competitive with inductive effects

[en] Short communication

[en] The integrals over the intermolecular trajectory, relevant to pressure-broadening and energy transfer calculations, are evaluated for the classical path, straight path, and distorted wave approximations. The present work, coupled with previous published work, leads to the conclusion that the three approximations agree to within 25% for near-resonant collisions involving reduced energies E*approximately-greater-than1. For nonresonant collisions the classical calculation, which does not conserve energy, is in surprisingly good agreement with the distorted wave results even when the energy mismatch is one-half of the incident energy

[en] Second and fourth order Markovian (M) and non-Markovian (NM) equations were solved analytically for stochastic treatment of collinear collision between two identical diatomic molecules. It is shown that when v/2ωL<<1 is satisfied the Markovian approximation (omission of memory) is sufficiently valid and all four approximation methods (2M, 4M, 2NM, 4NM) show good agreement with exact semiclassical theory. Convergence of the transition probabilities vs perturbation expansion of potential is slow and nonmonotonic. However, case by case, non-Markovian approximation gives a faster convergence than the Markovian

[en] A new version of Johnson's log derivative method for integrating the (nonreactive) Schrodinger equation is described. The new feature is that the log derivative equation is integrated inward (from large r to small r) with initial conditions that correspond to asymptotically incoming (or outgoing) radial waves. The result is that the log derivative function Q(r) (which is now a complex function of r) is a very smooth, nonsingular function (compared to the oscillatory, singular behavior of Q(r) with the usual real boundary conditions), meaning that many fewer grid points are required for its numerical integration. The number of grid points necessary to achieve a given level of accuracy is also only a weak function of the scattering energy E or the mass of the particles. Test calculations for a one-dimensional and a multichannel example illustrate this behavior

No abstract available

[en] Spherical stellar systems, from globular star clusters to compact galaxy clusters, appear to be dynamically relaxed. In galaxies and galaxy clusters, collisional relaxation acts too slowly to produce the observed result; and a new argument suggests that the same may be true of globular star clusters. 'Violent relaxation' requires special initial conditions and seems unable to produce sufficiently extended halos. It is here proposed that dynamical relaxation may result from tidal perturbations by external systems. If this explanation is correct, it has important implications for the early history of galaxies and galaxy clusters. (author)

[en] Shows that the scattering of molecules yields much information on the intermolecular potential. Wave mechanical effects are involved but the De Broglie wave length is short in relation to the collision distance. Formulae for intermolecular potentials are stated, and graphs show some potentials. The technique of measuring the potentials by means of scatter experiments with intersecting beams of molecules is explained. (J.S.)

[en] A method for evaluating complex semiclassical first- and higher-order phase integrals is derived and tested. The method is an extension and generalization of an earlier procedure devised for evaluating real phase integrals. The semiclassical approach is tested by calculating first- and higher-order complex phase shifts. It is shown that the first-order results often are too inaccurate, but the accuracy in third order typically is sufficient and that the higher-order terms readily give reliable estimates of the accuracy achieved