The generalized cumulant expansion approach to stochastic reductions in molecular collision dynamics: Applications to collisional energy transfer

Journal Article · Wed Jun 01 04:00:00 EDT 1977 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.433785· OSTI ID:7216442

Schatz, G C

A generalized cumulant expansion method is developed for applying stochastic reductions to molecular collision processes. We begin by introducing an approximate partitioning of a collision system into two subsystems S/sub r/ and S/sub i/ which are assumed to be weakly correlated. Cumulant expansion methods are then used to simultaneously perform a stochastic reduction over S/sub i/, and a projection of the diagonal elements of the reduced density matrix for S/sub r/ thereby leading to a Pauli master equation describing S/sub r/. We then apply this general equation using an impulse approximation partitioning to problems in inelastic V--T and R--T scattering. For He+H/sub 2/ vibrationally inelastic collisions, the stochastic theory predicts low order moments and some probabilities in very good agreement with exact quantum results. In applications to He+H/sub 2/ rigid rotor scattering, integral cross sections and opacity functions within 10%--30% of exact results are obtained at most energies.

• Research Organization: Department of Chemistry, Northwestern University, Evanston, Illinois 60201
• OSTI ID: 7216442
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 66:11; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
COLLISIONS
CROSS SECTIONS
CRYOGENIC FLUIDS
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
FLUIDS
HELIUM
HYDROGEN
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
NONMETALS
RARE GASES
ROTATIONAL STATES
STOCHASTIC PROCESSES
VIBRATIONAL STATES