Infinite order sudden approximation for rotational energy transfer in gaseous mixtures
Rotational energy transfer in gaseous mixtures has been considered within the framework of the infinite order sudden (IOS) approximation. A new derivation of the IOS from the coupled states Lippmann--Schwinger equation is given. This approach shows the relation between the IOS and CS T matrices and also shows in a rather transparent fashion Sencrest's result that the IOS method does not truncate closed channels but rather employs a closure relation to sum over all rotor states. The general CS effective cross section formula for relaxation processes is used, along with the IOS approximation to the CS T matrix, to derive the general IOS effctive cross section.Factorization permits one to calculate other types of cross sections if any one type of cross section has been obtained by some procedure. The functional form can also be used to compact data. This formalism has been applied to calculate pressure broadening for the systems HD--He, HCl--He, CO--He, HCN--He, HCl--Ar, and CO/sub 2/--Ar. To test the IOS approximation, comparisons have been made to the CS results, which are known to be accurate for all these systems. The IOS approximation is found to be very accurate whenever the rotor spacings are small compared to the kinetic energy, provided closed channels do not play too great a role. For the systems CO--He, HCN--He, and CO/sub 2/--Ar, these conditions are well satisfied and the IOS is found to yield results accurate to within 10%--15%.
- Research Organization:
- Department of Physics, University of Houston, Houston, Texas 77004
- OSTI ID:
- 7077169
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 67:9; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Utility of the CS and IOS approximations for calculating generalized phenomenological cross sections in atom-diatom systems
Infinite-order-sudden method for light--heavy--light reactions: Application to D+HCl. -->. DCl+H
Related Subjects
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ARGON
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
COLLISIONS
CRYOGENIC FLUIDS
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
FLUIDS
HELIUM
HYDROCHLORIC ACID
HYDROCYANIC ACID
HYDROGEN
HYDROGEN COMPOUNDS
INORGANIC ACIDS
MOLECULE COLLISIONS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
ROTATIONAL STATES
SUDDEN APPROXIMATION