VIBRATION-ROTATION LINEWIDTHS OF HCl AND HF UNDER HIGH PRESSURES OF ARGON

$^{1}$J. Albers and I. Openheim, Physica 56, 187, 237 (1971). This work is supported by the National Science Foundation, Grant Number MPS73-04733A01. Present address of L. Marabella: Hughes Research Laboratory, Culver City, California, 90230Author Institution: Department of Chemistry, Massachusetts Institute of Technology, CambridgeWe have measured the widths of several low J vibration-rotation lines of the R branch of HCl and the P branch of HF perturbed by argon at pressures from 20 to 100 atmospheres. This was done using the tunable 2.5 to 3.5 micron infrared from an optical parametric oscillator. The widths measured in this pressure range were up to twenty percent narrower than the linear extrapolation of some low pressure measurements in the literature. Within our experimental accuracy, the lineshapes appear Lorentzian. Deviations from linearity of the dependence of the width on pressure may be explained by collisions involving three or more particles. Some estimates of higher order density contributions to the line-width can be made, using a formal theory of Albers and $Oppenheim^{1}$