Intrinsic Optical Absorption in Tellurium

Measurements of intrinsic optical absorption have been made at 100 and 300^∘{}K by transmission techniques, covering a range of absorption coefficient from 0.01 cm^-1 to 1000 cm^-1 for radiation polarized E{∥}C, and to 5000 cm^-1 for E {⊥} C. These results suggest that the edge is set by vertical transitions, the transition being allowed for the polarization E {⊥} C but forbidden for E{∥}C. Absorption above the intrinsic threshold is apparently influenced by electron-hole interaction, as postulated by Elliott. In the actual edge region, absorption falls off exponentially with decreasing photon energy, the steepness at 300^∘{}K being 197 eV^-1 for E{∥}C and 267 eV^-1 for E {⊥} C. The steepness for each polarization increases by only 14% on cooling to 100^∘{}K.