title: Zero Kinetic Energy Photoelectron Spectroscopy of Benzo[h]quinoline.
abstract: We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[h]quinoline (BhQ) via resonantly enhanced multiphoton ionization (REMPI) through the first electronically excited state S1. From the simulated REMPI spectra with and without Herzberg-Teller coupling, we conclude that vibronic coupling plays a minor but observable role in the electronic excitation to the S1 state. We further compare the S1 state of BhQ with the first two electronically excited states of phenanthrene, noticing a similarity of the S1 state of BhQ with the second electronically excited state S2 of phenanthrene. In the ZEKE spectra of BhQ, the vibrational frequencies of the cationic state D0 are consistently higher than those of the intermediate neutral state, indicating enhanced bonding upon ionization. The sparse ZEKE spectra, compared with the spectrum of phenanthrene containing rich vibronic activities, further imply that the nitrogen atom has attenuated the structural change between S1 and D0 states. We speculate that the nitrogen atom can withdraw an electron in the S1 state and donate an electron in the D0 state, thereby minimizing the structural change during ionization. The origin of the first electronically excited state is determined to be 29,410 ± 5 cm(-1), and the adiabatic ionization potential is determined to be 65,064 ± 7 cm(-1).
authors.affiliation: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors.forename: Colin
authors.initials: C
authors.lastname: Harthcock
authors.affiliation: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Kong