Evaluation of the Intermolecular Potential Well Depth from Observations of Rainbow Scattering: Cs–Hg and K–Hg

Abstract

P(31 P( II R(OI R(21 R(41 R(SI R(SI FIG. 1. Pressure-induced shifts of lines in the 2-{) band of HCl due to xenon; at four temperatures.cell length was 30 em for the observations at -77°C and 50 em for the others.The procedure for measuring the shifts was similar to that already described. 3The reference cell contained a small quantity of HCI only, and was at room temperature.The results are presented in the figure as shifts for a constant density of xenon.In impact theories,4 collisions with an impact parameter smaller than a certain critical value b o are treated as "strong."While affecting linewidth, these strong collisions do not contribute to the shift.If it is assumed that the interaction energy is proportional to the inverse sixth power of the intermolecular distance, impact theories suggest that for lines with small J numbers, for which b o can be shown to be large, the shift should be proportional to T3/lo.For high values of J, b o can be shown to be smaller, and a statistical factor arising from the intermolecular potential may play an important role.This factor favors closer collisions, leading to larger shifts, but since it decreases in importance with increasing temperature, it may be the cause of the reversal, at high J numbers, of the direction of the temperature dependence that seems to be apparent in Fig. 1.