Transmission spectra of synthetic and natural hematite (α-Fe2O3) crystals are measured at temperatures 10, 25, and 300 K in the wavelength range 500–1100 nm, and the absorption spectra are computed. Pure exciton and exciton–magnon d–d transition bands are revealed, the corresponding wavelengths at 10 K being λ0=1020 nm and λ1=965 nm respectively. The half-widths and oscillator forces are g0=84 cm−1, f0=4×10−9, g1=60 cm−1, f1=1.4×10−7 for 10 K, g0=85 cm−1, f0=5×10−9, g1=110 cm−1, f1=2.1×10−7 for 25 K. The mechanisms of band formation for weakly allowed d–d transitions in hematite are analyzed.

The spectral features of the optical functions of the Drude model are investigated over wide ranges of parameters — the plasma frequency ωp of the current carriers, their transport relaxation frequency g, and the dielectric constant ε∞ due to high-energy electronic transitions in the system. The conditions are determined for: a) the square-root frequency dependence of the modulus and phase of the reflection; b) linearity of the phase θ=2ω/ωpε∞+θ0; c) the existence of a plasma reflection edge. Approximate relations are obtained which permit simplifying the analysis of optical reflection and electron characteristic energy loss data both in “good” metals and in materials with a strong temperature dependence of the electrical conductivity (semiconductors, doped and nonstoichiometric oxides, granular metal films, and amorphous alloys). The parameters of the systems of conduction electrons in Al and U2Zn17 are determined.

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