Prediction of the Cl(2 P 3/2)/Cl(2 P 1/2) branching ratio in the photodissociation of HCl

Abstract

The theory for the photodissociation of a diatomic molecule to particular levels of atoms possessing both spin and orbital angular momenta is presented. The theory has been applied to predict the Cl(2P3/2)/Cl(2P1/2) branching ratio in the A1Πâ†�X1Σ+ photodissociation of HCl. The repulsive excited electronic state potential-energy curve and the A1Πâ†�X1Σ+ transition dipole-moment function used in the calculation have been obtained from the inversion of the experimentally observed photodissociation cross-section. The multichannel scattering dynamics in the upper electronic state have been computed using the artificial channels method. The branching ratio is not statistical and varies with energy. For excited vibrational states, both the total integral photodissociation cross-section and the branching ratio show a quasi-periodic dependence with energy. This structure mirrors the nodal structure of the parent vibrational wavefunctions and the energy dependence of the branching ratio clearly demonstrates the dynamical curve crossings which occur during the break-up of the molecule.