State resolved rotational excitation in HD+D2 collisions. I. Angular dependence of 0→1 transitions

Abstract

In a crossed molecular beam experiment, time-of-flight distributions of HD molecules scattered from D2 have been measured at 42.2, 45.4, and 50.8 meV collision energy using the pseudorandom chopper method. In all cases rotational transitions of HD from j=0 to j=1 were resolved. At 45.4 meV complete differential cross sections have been generated from 10 ° to 120 °. They display well resolved diffraction oscillations in both the elastic 0→0 and inelastic 0→1 channels. Calculations show that these data essentially provide information on the position and the slope of the isotropic H2–H2 interaction potential near the zero point. The comparison between measurement and close coupling calculations based on the ab initio potential surface of Meyer and Schaefer shows a remarkable agreement. Only very small deviations in the positions of the diffraction oscillation extrema occur giving rise to a slight modification of the repulsive wall near the zero point. It has to be shifted by 0.1 Å to give a perfect fit to the measured data.