Simulation of ultrafast photodynamics of pyrrole with a multiconfigurational Ehrenfest method.

We report the first results of ab initio multiconfigurational Ehrenfest simulations of pyrrole photodynamics. We note that, in addition to the two intersections of 1(1)A2 and 1(1)B1 states with the ground state 1(1)A1, which are known to be responsible for N-H bond fission, another intersection between the 1(2)A2 and 1(2)B1 states of the resulting molecular radical becomes important after the departure of the H atom. This intersection, which is effectively between the two lowest electronic states of the pyrrolyl radical, may play a significant role in explaining the branching ratio between the two states observed experimentally. The exchange of population between the two states of pyrrolyl occurs on a longer scale than that of N-H bond fission.