EXCITED ELECTRONIC STATES OF PROTONATED ACETYLENE .2. ANISOTROPY OF THE POTENTIAL-ENERGY SURFACE

Extensive ab initio configuration interaction calculations have been c arried out for different directions of approach of a proton to a rigid acetylene molecule. The calculated potential energy curves of several singlet states are presented. The anisotropy we found allows us to ex plain features of the charge transfer mechanism during proton-acetylen e collisions as observed in recent molecular beam experiments. An impo rtant theoretical conclusion is the preference of the linear approach of protons in collisions with acetylene for the formation of acetylene ions.