Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of benzo[e]pyrene

We report zero kinetic energy (ZEKE) photoelectron spectroscopy via resonantly enhanced multiphoton ionization (REMPI) for benzo[e]pyrene. Extensive vibronic coupling between the first electronically excited state and a nearby state allows b2 modes to be observed which would be Franck–Condon (FC) disallowed. These vibronic modes are comparable in intensity to the FC allowed a1 modes. We are able to qualitatively simulate the vibronic spectra of both REMPI and ZEKE using density functional methods. The ZEKE spectra demonstrate propensity in preserving the vibrational excitation of the intermediate state. These results suggest a remarkable structural stability of BeP in accommodating the additional charge.