A theoretical study of collinear scattering : I. A new method to calculate reactive and dissociative cross sections of atom plus diatom systems. II. A reexamination of the collinear inelastic collision of two diatomics

Citation

Dwyer, John Patrick (1976) A theoretical study of collinear scattering : I. A new method to calculate reactive and dissociative cross sections of atom plus diatom systems. II. A reexamination of the collinear inelastic collision of two diatomics. Master's thesis, California Institute of Technology. doi:10.7907/E5AG-JH44. https://resolver.caltech.edu/CaltechTHESIS:03292010-113051468

Abstract

In attempting to understand the nature of a chemical reaction, the theoretical chemist is severely limited. Exact quantum mechanical (EQM) 3-D calculations of all but the simplest chemical systems are prohibitively expensive. In addition, accurate potential surfaces are not available for most reactions. Finally, because the cost of computation increases with the collision energy, 3-D investigations are restricted to low energies. To circumvent these difficulties, one might develop approximate theories, or do exact calculations on model systems. The first method permits one to calculate cross sections for real chemical reactions, but it leaves one wondering if the results are correct, since experimental work is often not sophisticated enough to verify (or disclaim) them. The second method has the disadvantage of being "unreal". Cross sections for model systems may exhibit properties not found in the real system, while hiding or distorting properties which actually exist. However, EQM calculations on model systems are useful for testing approximate theories. In this thesis we present two calculations on model systems. The first is for the collinear collision of H and H_2 using a realistic potential surface. Although other investigations have calculated reactive and nonreactive cross sections for atom-diatom collisions, their results have been restricted to low energies and have not included dissociation as a possible reaction pathway. We present a general method for calculating reactive, nonreactive and dissociative cross sections for an atom-diatom collision and apply it to the H_3 surface. In part II we present transition probabilities for the nonreactive collinear collision of two identical diatoms. We use a model potential surface, but are able to compare our results to those of other investigators who used an approximate theory.

Thesis Files