Rotamers of 3,4-difluorophenol studied by two-color resonant two-photon mass-analyzed threshold ionization spectroscopy

We applied the resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibrational spectra of 3,4-difluorophenol in the first electronically excited and the ionic ground states. The band origins of the S-1 <- S-0 electronic transition of the cis and trans rotamers are found to be 35,486 +/- 2 and 35,704 +/- 2 cm(-1) and the adiabatic ionization energies are 70,016 +/- 5 and 70,203 +/- 5 cm(-1), respectively. The distinct spectral features mainly result from the in-plane ring deformation and substituent-sensitive bending vibrations. Spectral analysis suggests that the molecular geometry and vibrational coordinates of the cation in the D-0 state resemble those of the neutral species in the S-1 state for both cis and trans rotamers. (C) 2013 Elsevier B.V. All rights reserved.