R. Yamamoto et al., Vibrational spectra and relaxation of benzonitrile and its clusters using time-resolved stimulated Raman-UV double resonance spectroscopy, J RAMAN SP, 31(4), 2000, pp. 295-304
Raman spectra of ring-breathing (nu(12)) and CN stretching vibrations (nu(C
N)) of jet-cooled benzonitrile and its clusters with Ar, H2O, CH3OH, CH3CN,
CCl4, CHCl3 and CHF3 were observed by stimulated Raman-UV double resonance
spectroscopy. Cluster structures were determined on the basis of the obser
ved vibrational spectra, rotational contour analyses of the high resolution
S-1-S-0 electronic spectra and ab initio molecular orbital calculations wi
th the HF/6-31G(d,p) basis set. It was found that the types of the cluster
structures are classified into three groups. (1) The clusters with H2O, CH3
OH and CH3CN represent the 'side'-type structure, in which the intermolecul
ar bond is formed in the phenyl plane of benzonitrile, and the benzonitrile
dimer also belongs to this structure. (2) The clusters with Ar and CCl4 fo
rm the 'on-top'-type structure, where Ar or CCl4 is located above the pheny
l plane. (3) The clusters with CHCl3 and CHF3 have the 'linear'-type struct
ure, in which these molecules are located at the N end of the CN group of b
enzonitrile. The rate constants of the vibrational relaxation for these clu
sters occurring after the Raman excitation to their nu(12) vibrations were
also observed. It was found that different rate constants are associated wi
th the different types of cluster structures. That is, the 12(1) levels of
the 'side'-type clusters relax much faster than those of other types of the
clusters. The results represent a clear indication that the anharmonic cou
pling between nu(12) and intermolecular vibrations are much larger in the '
side'-type clusters than others. Copyright (C) 2000 John Wiley & Sons, Ltd.