Isotope effects in Raman spectra of crystalline sulfur $\alpha$-$\mathrm S_8$

The Raman spectra of $^{32}\mathrm S$, $^{33}\mathrm S$, and $^{34}\mathrm S$ powders, as well as $^{\text{natur}}\mathrm S$ powder with the natural isotopic composition, have been measured in the temperature range of $5$–$300$ K. The isotope mass dependences of the vibrational frequencies have been obtained. It has been shown that such a dependence in the region of mixed translational-librational modes differs from the dependences known for monatomic inorganic crystals. The role of zero-point vibrations for low- and high-frequency modes has been revealed throughout the entire temperature range.