Vibrational spectroscopy and dynamics in the CH-stretch region of fluorene by IVR-assisted, ionization-gain stimulated Raman spectroscopy

J Phys Chem A. 2007 Dec 13;111(49):12466-70. doi: 10.1021/jp075053i. Epub 2007 Oct 9.

Abstract

We report stimulated Raman spectra at 0.2 and 0.03 cm(-1) resolution in the CH-stretching region of jet-cooled fluorene. The results were obtained by a version of ionization-gain stimulated Raman spectroscopy in which resonant two-photon ionization probing of the state-population changes arising from stimulated Raman transitions is assisted by the process of intramolecular vibrational redistribution (IVR) in the Raman-excited molecule. The fluorene spectra reveal extensive vibrational coupling interactions involving both the aliphatic and aromatic CH-stretching first excited states with nearby background states. Results pertaining to the symmetric aliphatic CH-stretching fundamental are consistent with a tier model of IVR and point to vibrational energy flow out of the CH stretch on a approximately 1 ps time scale with subsequent redistribution on a approximately 5 ps time scale.