The optical absorption of indium

Measurements of the optical conductivity of indium have been made in the energy range 0.5 to 3.8 eV. Films were evaporated and maintained in vacua<or=5*10-10 Torr. Optical data were obtained via ellipsometry with specimen temperatures 298, 200 and 140 K. In addition to a prominent peak in interband conductivity at 1.4 eV weak structure was observed at 2.15 eV in low temperature measurements. A temperature shift of the main absorption peak was observed, its effect being larger than expected on a simple pseudopotential diffraction model. The spectral features at 1.4 and 2.15 eV are in good agreement with recent band structure calculations.