Intensity Distribution in the Sideband Spectrum of NO3in KI

Abstract
The 1400-cm1 absorption band of the nitrate impurity in potassium iodide shows at 4.2°K a considerable amount of fine structure. The intensity distribution of this fine structure is governed by the anharmonic coupling of the internal vibration of the nitrate ion with nearly unperturbed phonons. This distribution can be calculated satisfactorily by first-order perturbation theory.