Photodynamics of azomethane: a nonadiabatic surface-hopping study.

The internal conversion and hot ground-state dynamics of trans- and cis-azomethane starting in the S(1) state have been investigated by nonadiabatic ab initio surface hopping dynamics using MCSCF-GVB-CAS and MRCISD methods and by determining energy minima and saddle points, minima on the crossing seam, and minimum energy pathways on the ground and first excited-state surfaces. The lifetimes and photoproducts from the dynamics simulations, geometric properties, excitation energies of selected stationary points and minimum energy pathways between them are reported. Our results favor a statistical model with trans-AZM moving to the ground-state minima before the first CN dissociation takes place. A detailed discussion in comparison to recent experimental and theoretical data is presented.