Magnetic transitions and the interpretation of the partial wave parameter in the CS and IOS approximations in molecular scattering theory

Journal Article · Wed Nov 15 04:00:00 EST 1978 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.436432· OSTI ID:6537035

Khare, V; Kouri, D J; Pack, R T

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-barj/sub 0/m/sub 0/), 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.

• Research Organization: Departments of Chemistry and Physics, University of Houston, Houston, Texas 77004
• OSTI ID: 6537035
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 69:10; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ANGULAR MOMENTUM
COLLISIONS
CROSS SECTIONS
ENERGY-LEVEL TRANSITIONS
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
PARTIAL WAVES