The infrared spectrum of crystalline p-chloroaniline at low temperature

High resolution spectra of oriented polycrystalline films of p-chloroaniline were recorded at a nominal temperature of 20 K using polarized infrared radiation and interpreted on the basis of the reported crystal structure. The observed spectra are characteristic of an [hkl] crystal plane. The crystal frequencies are classified into the three infrared active factor group symmetry species B1u, B2u, and B3u of the D2h factor group, having electric dipole moment vectors along the crystal axes a, b, and c, respectively. The symmetry types of the internal molecular modes are determined on the basis of the intensity patterns of their Davydov components and correlation between the molecular and factor groups. Some of the vibrational assignments are discussed.