Time-dependent quantum wave-packet description of the 1πσ* photochemistry of pyrrole

The photoinduced hydrogen elimination reaction in pyrrole via the conical intersection of the B-1(1) ((1)pisigma*) excited state with the electronic ground state has been investigated by time-dependent quantum wave-packet dynamics. A two-dimensional model potential-energy surface has been constructed as a function of the NH stretching and the hydrogen out-of-plane bending mode, employing multi-reference ab initio electronic-structure methods. The branching ratio of the reactive flux at the conical intersection has been investigated in dependence on the initial vibrational state of the molecule. The results suggest that laser control of the photodissociation of pyrrole via mode-specific vibrational excitation should be possible.