Rotational relaxation and excitation rates of hydrogen fluoride in collision with ortho- and para-H2

Abstract

We report de-excitation (and excitation) rate coefficients based on previous time-independent close-coupling scattering calculations for the rotational transitions of the hydrogen fluoride (HF) induced by collision with the two nuclear spin isomers ortho- and para-H2. These calculations were realized with the use of a new global four-dimensional potential energy surface recently computed by our group. We consider transitions for HF rotational levels up to jHF= 7, and for H2 levels up to = 3 (ortho-H2) and = 2 (para-H2). Rates are calculated for a range of temperatures up to 150 K. Our results show a strong difference of behaviour between ortho-H2 and para-H2 and validate the much stronger efficiency for the quenching of HF in collision with H2 in comparison with He.