Refractive index spectral dependence, Raman spectra, and transmission spectra of high-purity 72Ge, 73Ge, 74Ge, 76Ge, and natGe 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^-1 resolution and accuracy of 2×10^-5 to 1×10^-4 are shown. The content of 72 impurities measured by the mass spectrometric method was below 10^-5-10^-6 wt. %. Oxygen and carbon concentrations measured by IR spectroscopy in all crystals are within 5×10¹⁵ cm^-3. All germanium crystals have a hole conductivity with specific electric resistivity of 45-50 Ohm×cm. The coefficients of the generalized Cauchy dispersion function approximating the experimental refractive index values all over the measuring range are given. The transmission and Raman spectra are also given.