Abstract:
The spectra of the creation of the main emission bands at $3.65\div4.0$ eV and the long-wavelength emission bands at $3.0\div3.1$ eV, $2.6\div2.7$ eV, and $2.3\div2.4$ eV in $K_2SO_4$ crystals and $Na_2SO_4$ at temperatures of 15-300 K was investigated.
It is shown that these emissions are excited by low-energy photons with an energy of $4.6\div6.2$ eV, as well as high-energy photons of $6.4\div10.5$ eV. During excitation, electrons from $1t_1$,$3t_2$,e,$2t_2$ orbitals of the valence band transfer to the state of the cation in the conduction band. Holes arising in these orbitals, float to a level above the valence band and are localized. The main emission of $3.65\div4.0$ eV arises when electrons recombine with these localized holes located above the valence band.
