Refractive index spectral dependence, Raman spectra, and transmission spectra of high-purity Ge, Ge, Ge, Ge, and Ge single crystals.

The results of the precise measurement of the refractive index of stable germanium isotopes Ge72, Ge73, Ge74, and Ge76 single crystals with high enrichment and a germanium single-crystal Genat of natural isotopic composition with the Fourier-transform interference refractometry method from 1.94 to 20 μm with 0.1  cm resolution and accuracy of 2×10 to 1×10 are shown.