Effect of conical intersection of benzene on non-adiabatic dynamics

The effect of conical intersection on the excited dynamics of benzene is studied by ab initio theory of electronic structure, which provides an important insight into photophysical and photochemical reactions. Based on the CASSCF(6,6)/6-31+G(d, p) method, the topological structures of conical intersections S-1/S and S-2/S-1 of benzene, as well as the optimal structures of the ground state (S) and excited states (S-1, S-2), are determined. The energy minima of the S-1 state and S-2 state are estimated at 4.608 eV and 6.889 eV, respectively. In addition, the energy values of the conical intersections of S-1/S and S-2/S-1 are predicted to be 5.600 eV and 6.774 eV. According to the topological structures and energy values of the S-2/S-1 and S-1/S conical intersections, the photophysical behavior of benzene excited to the S-2 state and the effects of the S-2/S-1 and S-1/S conical intersections are discussed in detail.