Ultrafast dynamics through conical intersections and intramolecular vibrational energy redistribution in styrene

We report a femtosecond time-resolved photoelectron spectroscopy (TRPES) investigation of internal conversion in the first two excited singlet electronic states of styrene. We find that radiationless decay through an S-1/S-0 conical intersection occurs on a timescale of similar to 4 ps following direct excitation to S-1 with 0.6 eV excess energy, but that the same process is significantly slower (similar to 20 ps) if it follows internal conversion from S-2 to S-1 after excitation to S-2 with 0.3 eV excess energy (0.9 eV excess energy in S-1).