Infrared Optical Constants of NaCl

Abstract

The infrared optical constants of NaCl are calculated by applying an extended form of the Born and Blackman anharmonic potential theory to the Kellerman model of the NaCl crystal. A damping factor is derived which depends on the amplitudes and frequencies of the characteristic modes as well as on the frequency of the incident radiation. By a numerical sampling of wave vector space, this damping factor and the resultant optical constants are calculated in the range 25μ—500μ. The theory predicts a subsidiary absorption maximum near 100μ which agrees with recent experimental measurements. The frequency distribution function of NaCl is also given here.