Multiphonon optical spectrum of NaF

The high-frequency exponential wing of the reststrahlen band of NaF is decomposed into a number of N-phonon absorption spectra (N=2,3,4,5) by means of a temperature analysis. Overall agreement of the individual spectra with recent theoretical predictions is good, except for a fairly pronounced structure which indicates particularly strong contributions from certain frequencies of the TO and LO phonon branches. © 1974 The American Physical Society.