Line shape cross sections of HD immersed in HE and H2 gas. I. Pressure broadening cross sections

Abstract

The R(0) and R(1) line shapes of HD are of interest because observation of these lines in the atmosphere of the outer planets should lead to unambiguous values of the D/H ratio. The electronic potential energy surfaces used to calculate HD–He and HD–H2 line shape cross sections have been well validated in previous publications of this series. The results of two additional tests of the electronic potential energy surface of hydrogen-like systems are reported here: the second virial coefficient of para-hydrogen at low temperatures and HD–D2 elastic and inelastic differential scattering cross sections. Formulas are given for Dicke narrowing as well as for the line broadening and shift cross sections calculated here. Close coupling calculations were carried out for the R(0) and R(1) transitions of HD immersed in He and for the R(0) transition of HD immersed in H2. These cross sections are anticipated to be quite reliable at temperatures above 50 K, i.e., where clustering can be ignored.