Excited-State Dynamics in SO2: II. The Role of Triplet States in the Bound State Relaxation Studied by Surface-Hopping Simulations

TL;DR

This study uses surface-hopping simulations to reveal that triplet states significantly influence SO2's ultrafast photorelaxation, with intersystem crossing competing with internal conversion on a sub-picosecond timescale.

Contribution

It demonstrates the critical role of triplet states and spin-orbit coupling in SO2's excited-state dynamics using advanced mixed quantum-classical simulations.

Findings

Intersystem crossing occurs within a few hundred femtoseconds.

Triplet states participate actively in the relaxation process.

Population transfer dynamics differ markedly when triplet states are included.

Abstract

The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the Surface Hopping including ARbitrary Couplings (Sharc) method, intersystem crossing processes caused by spin-orbit coupling are found occuring on an ultrafast time scale (few 100 fs) and thus competing with internal conversion. While in the singlet-only dynamics only oscillatory population transfer between the 1B1 and 1A2 states is observed, in the dynamics including singlet and triplet states we find additionally continuous ISC to the 3B2 state and to a smaller extent to the 3B1/3A2 coupled states. The populations obtained from the dynamics are discussed with respect to the overall nuclear motion and in the light of recent TRPEPICO studies [Wilkinson et al., paper I].