Knowledge Bank

The infrared spectra of gaseous ClCN and BrCN at room temperature have been determined in the LiF, NaCl, KBr, and CsBr prism regions. Several upper stage bands, as well as bands due to $C13$, have been identified. From the assignments, a number of the vibrational constants have been evaluated and the Fermi resonant levels treated by a first order perturbation method. The infrared spectra of crystalline ClCN, BrCN, and ICN show isotopic bands due to $C13$ and to $N15$. The spectra are discussed in terms of the available x-ray crystal data.