II. The lattice resonances of ionic crystals

Abstract

Abstract Sixteen crystalline ionic halides have been studied in transmission and reflexion experiments in the range 70 to 250μ at temperatures down to 4 °K. The lattice resonances have been clearly observed, their characteristic frequencies accurately determined and the degree of damping investigated as a function of temperature. The significance of the results is discussed from the point of view of various models of dielectric behaviour—in particular the refinements of the Born-Lorentz model which cover the effect of distortion moments due to the overlap of neighbouring ions. Discrepancies remain between theory and experiment which have a bearing on the calculation of vibration spectra.