Raman Scattering with Multiphonon Process in Single Crystal of α-NiSO₄·6H₂O

Abstract

The Raman spectrum of α-NiSO₄·6H₂O was obtained at room temperature and 77 K. A theoretical study of the number, type and activity of the optical phonons in this material permitted a classification of the observed phonons. The data showed an anomalous temperature dependence for the peaks at 75 and 115 cm⁻¹ with symmetry A₁. The Raman spectrum (0 to 150 cm⁻¹) of the B₂ phonons at several temperatures from 77 K to room temperature was also obtained. The line at 42 cm⁻¹ at T=300 K has a temperature dependence characteristic of difference combination of two other phonons. Another line of the same symmetry, which would be the sum combination of those two phonons, has a temperature dependence of its intensity characteristic of a one phonon line.