Quantum dynamical calculations for the vibrational predissociation of the He–ICl complex: Product rotational distribution

Abstract

Three-dimensional quantum close-coupling calculations are presented for the vibrational predissociation of He–ICl B state complexes containing two quanta of ICl vibrational excitation. The dynamics are evaluated for the lowest quasibound van der Waals levels of He–ICl with total angular momentum J=0 and 1. The vibrational predissociation lifetime and final ICl B(v=1, j ) rotational distribution are calculated using the golden rule approximation. The calculated ICl product rotational distributions are broadly bimodal with maxima at j=7 and 15, as experimentally observed. The computed rotational distributions exhibit pronounced oscillations, which are expected to be suppressed when averaged over the initial angular momentum distribution sampled in the experiment. The theoretical analysis points to the dominant role of final-state interactions in determining the rotational distribution of the ICl fragments. The zero-point bending motion of the He–ICl complex and the coupling between the initial and final vibrational states make only small contributions to the final ICl rotational-state distributions. The extensive rotational excitation of the ICl product is primarily due to the anisotropic intermolecular interaction between the separating ICl and He fragments.