Semiclassical treatment of the photofragmentation of azomethane

We have studied the photofragmentation of azomethane by classical trajectories plus surface hopping, run on ab initio potential energy surfaces. Transition probabilities are evaluated with the help of a general diabatization technique. The radiationless transition from S1 to S0 occurs within 0.5 ps and the fragmentation takes place almost exclusively in the ground state. About 2/3 of the trajectories lead to almost simultaneous breaking of both N–C bonds, while 1/3 go through formation of the CH3NN⋅ radical; however, the latter breaks apart with a short delay of the order of 1 ps.