Internal and external heavy-atom effects on phosphorescence radiative lifetimes calculated using a mean-field spin–orbit Hamiltonian

We investigate the performance of an atomic mean-field approximation to the spin–orbit interaction Hamiltonian in calculations of phosphorescence radiative lifetimes. A comparison of the performance of the mean-field approximation with the full spin–orbit interaction operator is made for the phosphorescent radiative lifetimes of the 3B1u excited state of ethylene perturbed by an external halogen ion, and for the 3A1 and 3B1 excited states in mono- and di-halogen-substituted pyridines. The mean-field approximation is shown to give excellent results compared to calculations with the full one- and two-electron spin–orbit integrals.