Vibrational Relaxation in Liquid Phenylacetylene. 1

Raman and IR spectra of phenylacetylene dissolved in methylcyclohexane and acetonitrile have been recorded. The IR line widths and Raman isotropic line widths of totally symmetric A 1 vibrations of phenylacetylene the stretching mode of the ethynyl group C⋮C (ν S (C⋮C)), the phenyl ring in-plane stretching (ν 8a ), the C-phenyl group stretching (ν S (C−Ph)), and the phenyl ring breathing (mixed with trigonal vibration) (ν 12 ) have been recorded. The spectra have been measured as a function of concentration at room temperature. Theoretical models of vibrational dephasing have been tested and compared with experiment.