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 S1/S and S2/S1 of benzene, as well as the optimal structures of the ground state (S) and excited states (S1, S2), are determined. The energy minima of the S1 state and S2 state are estimated at 4.608 eV and 6.889 eV, respectively. In addition, the energy values of the conical intersections of S1/S and S2/S1 are predicted to be 5.600 eV and 6.774 eV. According to the topological structures and energy values of the S2/S1 and S1/S conical intersections, the photophysical behavior of benzene excited to the S2 state and the effects of the S2/S1 and S1/S conical intersections are discussed in detail. [ABSTRACT FROM AUTHOR]