The second order Raman spectrum of calcium fluoride

Abstract

The second-order Raman spectrum of calcium fluoride recorded recently by Russell, using a He-Ne laser source, is discussed in the light of current theories on the dynamics of crystals. The observed spectrum of CaF₂ is examined in detail with a calculation of the frequencies of the supercell modes using the lattice dynamic models of Ramanathan and Ganesan and Srinivasan, with the selection rules for the combinations from the critical points X for CaF₂ structures. Satisfactory explanations have been given for most of the observed second-order frequency shifts.