Fast Intersystem Crossing in Transition-Metal Complexes

TL;DR

This paper explains the rapid intersystem crossing in transition-metal complexes as a process driven by spin-orbit coupling and phonon dephasing, with decay times matching experimental observations.

Contribution

It introduces a detailed mechanism involving phonon dephasing and spin-orbit interaction that accounts for the fast intersystem crossing in transition-metal complexes.

Findings

Decay time matches experimental data

Fast decay occurs faster than phonon oscillation frequency

Slower decay observed at higher energies

Abstract

The mechanism behind fast intersystem crossing in transition-metal complexes is shown to be a result of the dephasing of the photoexcited state to the phonon continuum of a different state with a significantly different transition metal-ligand distance. The coupling is a result of the spin-orbit interaction causing a change in the local moment. Recurrence to the initial state is prevented by the damping of the phonon oscillation. The decay time is faster than the oscillation frequency of the transition metal-ligand stretch mode, in agreement with experiment. For energies above the region where the strongest coupling occurs, a slower "leakage-type" decay is observed. If the photoexcited state is lower in energy than the state it couples to, then there is no decay.