Infrared Spectrum of Crystalline CH2Cl2 and CD2Cl2. Polarization Measurements and Crystal Structure

Abstract

The infrared spectra of crystalline CH2Cl2 and CD2Cl2 were measured at temperatures ranging from 5 to 125°K and at 85°K, respectively, between 5000 and 200 cm−1. Splitting into two or more components was observed for several fundamentals. The mixed-crystal technique was used to prove the origin of the observed splittings, and the isotopic shifts for 37Cl and 13C as well as the factor-group splittings were identified. These data, together with polarization measurements on polycrystalline-oriented films, relative intensity measurements, and other independent data, such as crystal density and Raman spectrum, were used to determine the crystal structure. The data accumulated are consistent with an orthormbic D2h14(Pbcn) unit cell with four molecules located on C2 sites.