Non-adiabatic processes: non-orthogonal basis sets

Abstract

Numerical studies of non-adiabatic systems have been made using non-orthogonal basis functions in an attempt to reduce the basis size required for accurate solutions. The basis functions of totally symmetric “tuning modes” are chosen to be centered at the minima of each potential. Non-adiabatic coupling occurs mainly between combinations of basis functions which bridge the energy gap between the coupled potential energy surfaces. The size of the matrix needed to be diagonalized is reduced but only qualitative agreement is obtained with the full calculations.