Lattice vibrations and optical properties of β-rhombohedral boron in the far-IR region

The optical properties of single crystal β-rhombohedral boron have been determined by reflectivity and, additionally, partly by absorption measurements, from 10 cm-1 to 1450 cm-1. The lattice vibrations ranging from 170 to 1450 cm-1 could be attributed to one-phonon processes supplying the whole difference between the static and the optical dielectric constants. Split vibrations of the icosahedron, and vibrations of structural components in the spectrum have been separated, and a dispersion analysis yields the oscillator constants. At higher temperature, the frequency shift can be attributed to the Grueneisen shift. (Auth.)