Absolute Absorption Intensities of the Librational Modes of ClCN and BrCN

Abstract

The absolute absorption intensities of the two infrared‐active librational modes in crystalline ClCN and BrCN have been measured. The sums of the intensities of the two modes were 750 ± 90 and 800 ± 140 cm mM−1 for ClCN and BrCN, respectively. A dipolar coupling model was used to compute the expected intensities and the contributions of dipolar interactions to the frequencies of these lattice modes. The evaluation of the lattice sums in the direct or reciprocal lattice is discussed. The calculated intensities were 970 and 835 cm mM−1 for ClCN and BrCN, respectively.