Infrared Spectra of Gaseous and Crystalline Cyanogen Halides

Abstract

The infrared spectra of gaseous ClCN and BrCN at room temperature are reported for the LiF, NaCl, KBr, and CsBr prism regions. Several upper stage bands as well as bands due to C¹³ appear in both spectra. Assignments are given, from which a number of the vibrational constants are evaluated and the Fermi resonant levels treated by a first‐order perturbation method. The spectra of crystalline ClCN, BrCN, and ICN at −180°C is also recorded. Absorption bands, including several due to C¹³ and N¹⁵, are assigned and the spectra are discussed in terms of the available x‐ray crystal data.