THE QUANTUM-MECHANICAL IMPULSE APPROXIMATION. APPLICATION TO ’ ‘fIBRATIONAL INELASTIC SCATTERKN ~.

The quantum-mechanical impulse approximation is applied to vibrational excitation of a diatomic molecute by collinear collision with a third atom. Our calculations are compared with other theoretical results (exact quantum-mechanical, semi-classical, classical) and with experimental data from O:-He collisions. 1. Introduction energies are measured in units of twice the ground-state energy of the molecule. The quantum-mechanical imp&e approximation (hereafter denoted by IA) has been introduced by Chew to describe n-d scattering [I]. A clear descrip