The multiphoton ionization spectrum of benzene

Abstract

A resonance seen in the multiphoton ionization spectrum of benzene at 391.4 nm is identified as a two‐photon resonance with a bound state at 51 085 cm⁻¹. This state has probable symmetry ¹E_1g or ¹E_2g as indicated by an active e_2g vibration. No other allowed two‐photon transitions are seen below this energy. Three‐photon resonances with the Rydberg states of benzene are seen and compared to the one‐photon absorption spectrum. The great similarity indicates a strong ¹A_1g component in the two‐photon virtual state. Two‐photon resonances with the ¹B_2u state agree with two‐photon fluorescence excitation spectra but show no diminution above the energy where fluorescence is quenched.