  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].
