Accurate Quantum Mechanical Decoupling Approximations for Molecular Scattering Theory

Recent work is reviewed on the theory of angular momentum decoupling approximations in inelastic molecular scattering theory. It is shown that the failure of these approximations is more extensive than previously believed, particularly for completely state-selected m-transitions. A new method is presented for systematically improving these approximations, which recouples the approximate solutions to first-order using the generalized distorted wave Born approximation. As an illustration of the generality of this new recoupling technique, formulae are derived for the corrections to the centrifugal decoupling, the energy sudden and the infinite-order sudden approximations. Completely state-selected differential and integral cross sections are computed under the centrifugal decoupling approximation and its first-order distorted wave correction for Ne + HD scattering at a total energy of 31.5 meV. Five choices of the partial wave decoupling parameter (including the three known ones) are studied. The numerical results show that with the partial wave parameter chosen to be the arithmetic mean of the initial and final l-quantum numbers, the corrected centrifugal decoupling approximation gives significantly more accurate inelastic differential and integral state-selected cross sections than its uncorrected counterpart.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Mclenithan, Kelly Daniel

• Chemistry, Physical

Identifier

(UMI)AAI8302933

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70200