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 symmetric modes to be observed which would normally be Franck-Condon (FC) disallowed. These vibronic modes are comparable in intensity to the FC allowed a1 modes. Gaussian 09 is able to qualitatively simulate the vibronic spectra of the REMPI and the ZEKE experiment using density functional methods. The ZEKE spectra demonstrate propensity in preserving the vibrational excitation of the intermediate electronic state. These results suggest a remarkable structural stability of BeP in accommodating the additional charge.