Fine Structure of the Optical Spectra of Bismuth Triiodide

Full sets of the optical functions of a BiI₃ crystal in the range 1–5 eV have been calculated from the experimental spectra ₁(E) and ₂(E) for the polarizations E c and E c at 300 K. The spectra of permittivity and volumetric characteristic losses have been decomposed into elementary components and their main parameters have been determined. A schematic representation of the nature of the basic maxima of transitions on the basis of the well-known theoretical calculations of the bands and spectra of reflection of the BiI₃ crystal has been suggested.