Lattice Vibrations and Infrared Properties of Yttrium Fluoride

Abstract
The lattice vibrations of orthorhombic YF3 have been analyzed in terms of their symmetry properties at special points in the Brillouin zone. The polarized infrared spectrum of YF3 has been obtained in the range 4-125 μm by measuring the infrared (ir) spectral emittance of oriented crystals at 4.2 and 77°K. Based on selection rules for one-phonon processes at q=0, the fundamental, ir-active phonons at the zone center have been assigned to their symmetry species.