The Raman spectra of crystalline sulphates of Ni and Mn

Abstract

The paper reports the results of investigations on the Raman spectra of NiSO₄·6H₂O (tetragonal and monoclinic forms), NiSO₄·7H₂O (orthorhombic) and MnSO₄·4H₂O (monoclinic). Using λ 2536·5 resonance radiation of mercury for excitation of the Raman effect, it has been possible to observe a large number of frequency shifts. The spectra exhibit striking differences between themselves and also a few characters of general similarity. These are largely explicable in terms of the crystal symmetry and structure of these substances. In all the cases studied, the internal frequencies of the sulphate ion exhibit multiplicities owing to the lowering of the symmetry of the SO₄ ion in the crystalline state and due to the number of ions present in the unit cell.