Infra-Red Absorption Spectra at Low Temperatures

Abstract

An infra‐red absorption cell for use at low temperatures is described. Use of the cell requires no modification of the optical system of the spectrometer. Spectra of several organic substances which are solid or liquid at room temperature have been recorded and the changes in spectrum on cooling to −170°C observed. The results show that there is no systematic narrowing of infra‐red absorption bands on cooling from room temperature to −170°C. The narrowing reported by previous workers is not of general occurrence but is restricted to certain compounds which undergo a change of state in this temperature range.