Ab initio three-dimensional atom-diatom reaction cross sections using hyperspherical coordinates and variational surface functions

Author: Cuccaro, Steven Andrew

Year: 1991

Degree: Dissertation (Ph.D.)

Advisor: Kuppermann, Aron

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/n1ec-7f47

Abstract

This thesis discusses the development of a symmetrized hyperspherical coordinate technique for the calculation of accurated differential cross sections in the reactive collision of an atom with a diatomic molecule in three-dimensional space. The hyperspherical methodology has the advantage that all regions of configuration space are treated equivalently; this allows the reduction of the reactive scattering problem to an equivalent inelastic scattering problem, which is both computationally simpler and more straightforward conceptually.

The hyperspherical methodology is discussed in detail, including the expansion of the scattering wavefunction in terms of a basis of local hyperspherical surface functions and the calculation of this basis set. The methods are applied to the H + H2 system (using the LSTH potential energy surface) and used to calculate scattering matrices and partial wave cross sections for this reaction up to a total energy of 1.6 eV. The results presented here include the geometric phase effect due to the conical intersection of the H3 system, along with a set of results which do not include this effect for comparison with the previous work in the field.

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