Hole-burning and stimulated Raman-UV double resonance spectroscopies of jet-cooled toluene dimer

The structure of toluene dimer generated in a supersonic jet has been investigated by hole-burning and stimulated Raman-UV double resonance spectroscopies. Hole-burning spectroscopy revealed that the broad electronic spectrum of the S-1-S-0 transition of the toluene dimer consists of two components due to two isomers at least. On the basis of the calculated result given by Schauer and Bernstein, the two isomers were attributed to a sandwich-shaped dimer and a T-shaped dimer, respectively. Accurate vibrational frequencies of three vibrations v(1), v(12), and v(18a) for toluene-hs, toluene-d(8), and the dimer were obtained by stimulated Raman-UV double resonance spectroscopy. It was found that the 12(1) level of bare toluene-h(8) is perturbed by the vibration involving methyl rotation and its perturbation is reduced upon the dimer formation.