Rotational distributions from resonant and direct scattering in H+CO and tests of statistical theories

Abstract

Coupled-channel scattering calculations are reported for H+CO using an ab initio potential energy surface. Rotational state-to-state transition probabilities are presented for resonant and direct scattering for J=0 and treating CO as a rigid rotor. The presence of a barrier to complex formation in this system is found to have a crucial role in determining which asymptotic rotational states couple strongly to the resonances. In addition, a propensity for even-Δj transitions is seen for direct scattering and also for rotational states which do not couple to the resonances for resonant scattering. The features of the potential surface which are responsible for these results are uncovered by using distorted wave Born and Franck–Condon approximations. Tests of phase space theory and the statistical adiabatic channel model are made for resonant scattering. One important conclusion of these tests is that the bending motion of the HCO transition state is apparently not adiabatic.