Theoretical study of the U.V. spectrum of acetylene

Abstract

A method for the treatment of the Renner-Teller effect in Π and Δ electronic states of tetraatomic molecules is developed. It is based on a matrix representation of the vibronic hamiltonian in a basis consisting of products of electronic wavefunctions and the eigenfunctions of two two-dimensional harmonic oscillators. The method is used for calculation of the vibronic structure of the 1 ¹Π _u and the 1 ¹Δ _g electronic states of acetylene, whereby ab initio CI potential surfaces are employed.