The nature of intrinsic luminescence in CaSO 4 and K 2 SO 4 crystals Abstract. Based on the results obtained in the study of intrinsic short-wavelength emissions whilst excited by high-energy photons of 10,3 eV and 12,4 eV at 15 K by vacuum-ultraviolet spectroscopy, a model of intrinsic short-wavelength emissions for CaSO 4 and K 2 SO 4 is proposed.