Features of the infrared reflection spectra of SmS semiconductor in the homogeneity range

Infrared reflection spectra in the range of 5200–380 cm^?1 were measured for polycrystalline samarium monosulfide samples in the semiconductor phase with compositions Sm_{1 + x} S lying within the homogeneity range (0 ≤ x ≤ 0.17) in the temperature range of 300–600 K. Five peaks with energies in the range of 1150–880 cm^?1, whose positions depend weakly on the composition and temperature. It was shown that the reflection peaks are associated with ⁷ F ₀–⁷ F ₂ transitions of 4f electrons of Sm²⁺ ions.