Dynamics of acetone photodissociation: a surface hopping study

We present on the fly surface hopping simulations of the dynamics of photoexcited acetone in the n -> pi* band, taking into account both the spin-orbit and the dynamic couplings and allowing for the C-C bond dissociation. The S-0, S-1, T-1 and T-2 states were considered and the propagation time was 50 ps. According to the simulation results, after excitation to S1 both Internal Conversion (IC) to S-0 and InterSystem Crossing (ISC) to T-1 or T-2 take place at comparable rates; T-2 plays an important role and the simultaneous treatment of the spin-orbit and dynamic couplings is shown to be mandatory to describe the photodynamics. We propose a mechanism that explains the observed fast and slow decay rates of the S-1 state of acetone.