Recombination luminescence in alkali metal sulfates

In this paper we present the results of investigation of the nature of intrinsic luminescence caused by photon excitation in a wide spectral range from 10.3 eV to 4 eV at a temperature of 15-300 K. It is shown that in alkali metal sulfates the main emission band formed after excitation by X-rays and photons with an energy of 9-11 eV and 4-7.5 eV at 15-300 K is located in the spectral range of 3.65-3.9 eV. When the sulfates are excited by 4-7.75 eV photons, in addition to the emission band at 3.65-3.9 eV the other effective long-wave band at 3.1-2.5 eV appears. It is assumed that the 3.65-3.9 eV radiation results from the recombination of electrons with unevenly located holes of SO4− type. The long-wave emission bands in the alkali metal sulfates may be connected with the formation of electron-hole trapping centers after irradiation by photons with energies above 4.4 eV.