Time-resolved photoelectron spectroscopy from first principles: excited state dynamics of benzene.

We use the ab initio multiple spawning (AIMS) method to follow the dynamics of benzene after excitation to the second singlet excited state (S2). The results are validated by comparison to potential energy surfaces including dynamical electron correlation effects. Time-resolved photoelectron spectra are computed and compared to experimental results. Simulations agree with experiment that there are both short-lived and long-lived components of the excited state population. We show that these components both originate from quenching through the same S2/S1 conical intersection and that the difference between them comes from their behavior immediately after decay to S1. This is presumed to be a function of the details of the way in which the S2/S1 intersection region is accessed; for example, the momentum distribution and the topology of the seam in the relevant region.