Absolute Infrared Intensities in Crystalline Benzene

Abstract

The infrared spectra of polycrystalline benzene and fully deuterated benzene have been examined under high resolution. All ``u'' fundamentals (except ν16 of C6D6) have been observed and most crystal multiplets have been resolved, many to the full extent predicted. Accurate frequencies at two low temperatures are presented. Absolute intensities have been measured at two temperatures for all fundamentals observed. An interference method has been used to measure sample thickness. The results are compared to existing data on three phases of benzene. The sum of all integrated intensities for a given molecule is empirically found to be independent of state of aggregation, and a sum rule expressing this fact is derived and criticized.