Very low temperature helium pressure broadening of DCl in a collisionally cooled cell

Abstract

Very low temperature pressure broadening parameters and cross sections for the J=0–1 rotational transition of DCl broadened by helium are presented. Data was taken using a collisionally cooled cell and measured cross sections range from 10.76 Å2 at 4.21 K to 8.10 Å2 at 1.85 K. This compares with a 300 K cross section of 9.36 Å2. Predictions from two currently available anisotropic He–DCl potentials do not reproduce accurately the experimental results. Modifications were made to one of these potentials to reproduce more accurately both the observed low temperature and 300 K pressure broadening cross sections. The resulting modified potential has a well depth De=32.7 cm−1 at a separation Re=3.46 Å in the linear He–Cl–D configuration.