AbstractIn order to confirm the assignment of the Raman active internal modes of K2SO4and structurally related crystals, the Raman spectra of oriented cyrstals have been recorded. Using the relative integrated intensities of the bands as data, the transferability of the Raman tensors of the free SO 4−−ion to the crystals was investigated with, in general, good agreement between the calculated and measured intensity distribution. A linear dependence between the frequencies of the internal modes of the K2SO4, Rb2SO4and Cs2SO4crystals and the electronegativity of the cations could be observed. Also, a brief discussion about the nature of the lattice modes of these crystals is inc