Intermolecular Spectrum of Liquid Biphenyl Studied by Optical Kerr Effect Spectroscopy

Abstract

The intermolecular spectra of neat liquid biphenyl and biphenyl/n-heptane mixtures were obtained by using optically heterodyne detected optical Kerr effect (OHD-OKE) spectroscopy. The intermolecular spectrum of biphenyl is broad and bimodal in character. The spectrum of biphenyl undergoes a red shift and line narrowing with temperature and upon dilution in n-heptane. The spectra can be well fit by a bimodal line shape function. Inconsistencies, however, arise in the interpretation of the effects of temperature and dilution on the individual component bands. The spectrum of biphenyl is similar in frequency and width to that of benzene. Packing models suggest that rotational motion is more hindered in biphenyl than in benzene, which could explain the similarity of the spectra of the two liquids, even though the moments of inertia for the two molecules are quite different.