About the origin of the emission bands in the wavelength range 320-600 nm in KBr crystal at low temperatures

Abstract

In this paper the results of the registering of X-ray luminescence spectra of KBr crystal at the temperature range 10-325 K were presented. The spectrum of X-ray crystal KBr is composed of three bands - at ~ 280 nm (~ 4.44 eV) ~ 340 nm (~ 3.65 eV) and ~ 490 nm (~ 2.54 eV). The peak at 490 nm – π-luminescence from the triplet state excitons. In article the temperature dependence of  this band was explained by the theory of excitons self-trapping. The luminescence intensity of this band increases to 25 K then decreases. We have modeled by the continual theory that the potential barrier height of excitons self-trapping is minimal at a temperature of 25 K. So the theory confirms with experiment. The band at 280 nm eV – - luminescence from the singlet state exciton, reaches its maximum at low temperatures. The nature of the band at 340 nm eV is associated with the creation of excitons with more "symmetric" configuration than «strong-off».