Table of Contents
Laser Chemistry
Volume 14, Issue 1-3, Pages 131-141

Threshold Ionization Spectroscopy of the Low Frequency Vibrational Modes of Styrene and Trans-Stilbene Cations

Department of Chemistry, Wesleyan University, Middletown 06459, CT, USA

Received 6 May 1993

Copyright © 1994 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


High resolution photoelectron spectra are reported for styrene and stilbene with an emphasis on identifying the low frequency modes which are important in the phenyl–vinyl torsional motion. In the styrene cation three low frequency out-of-plane vibrations are measured, ν42, ν41 and ν40 as well as a number of higher frequency in plane modes. Generally the low frequency modes do not appear with significant intensity but by pumping the appropriate modes in the S1 intermediate state the intensity for these modes in the threshold ionization spectrum is quite good. In the stilbene cation the analogous phenyl–vinyl torsion, ν37, is also measured as well as the related mode ν36. The ethylene torsional mode in stilbene is not observed. In both molecules the observed frequencies are used to relate the electronic structure of the cation to the S1 and S0 states of the molecule.