Semiclassical dynamic simulation of photon induced ring-opening of cyclohexadiene to hexatriene

A dynamical picture and the detailed changes in the structure for the ring opening reaction of cyclohexadiene (CHD) to form hexatriene (HT) are studied by a semiclassical electron radiation-ion dynamics (SERID) simulation. Following the simulated trajectory, the potential energy curves (PECs) of three lowest singlet states (S0, S1 and S2) have been calculated at the CASSCF/MRPT2 level with 6-31G* basis sets. Two non-adiabatic state-to-state transitions are found at 112 fs and 129 fs, which confirms the mechanism suggested in the Ref. [M. Garavelli, C.S. Page, P. Celani, M. Olivucci, W.E. Schmid, S.A. Trushin, W. Fuss, J. Phys. Chem. A 105 (2001) 4458].

The energy curves by CASSCF (6, 6)/MRPT2 calculations for the simulation path. A: S1-S2 conical intersection minimum. B: S1-S0 non-adiabatic transition.