Radiation defects in alkali metal sulfates irradiated by ultraviolet photons

In the present paper the formation of defects in LiKSO4 andK2SO4crystals after excitation by 4-11 eV photons at the temperature of liquid nitrogen was studied by the methods of thermal activation and vacuum-ultraviolet spectroscopy. It is shown experimentally that electron-hole trapping centers are formed as a result of capture of electrons and holes by anion complexes SO42− created by the transition of electrons from 1t1; 3t2; e; 2t2 orbitals in the valence band to the s-state of the cation in the conduction band. It is supposed that the formation of defects in LiKSO4 and K2SO4 crystals is caused by the dissociation of excited anion complexes, created by the transition of electrons from 1t1; 3t2; e; 2t2 orbitals in the valence band to free, antibinding orbitals 4t2∗ and 3a1∗ in the conduction band. In this case, stable electron SO3−va+e− and hole O3− trapping centers are formed.