Oscillator Analysis of LiF and MgO Reflectivity

Book excerpt: Classical oscillator theory is applied to the analysis of the fundamental lattice vibration reflectivity spectrum of LiF and MgO in the 200 to 800/cm wave-number range. For each material seven reflectivity curves, ranging from 7.5 to 1060K for LiF and from 8 to 1950K for MgO, are analyzed and the associated dispersion parameters as a function of temperature obtained. The reflectivity curves of both LiF and MgO can be fitted with two resonances at all temperatures. Resonance frequencies nu sub 1 and nu sub 2 are decreasing functions, whereas strengths 4 pi rho sub 1 and 4 pi rho sub 2 are increasing functions of temperature. At the higher temperatures, the width of the main resonance gamma sub 1 obeys a T91.0) power law for LiF and a T(1.5) LAW FOR MgO. In addition, optical constants, real and imaginary parts of the dielectric constant, and absorption coefficients are calculated as functions of wave number and temperature. A description of the classical analysis computer program is included, together with input requirements and FORTRAN IV listings. (Author).