Features of the action of an uniaxial deformation on the radiative annihilation of excitons in KBr crystal

Abstract

To study the effect of uniaxial deformation by 〈100〉 and 〈110〉 directions on the radiative annihilation of self-trapped excitons (STE), the experiments were carried out with KI, KCl and KBr crystals. At deformation by 〈110〉 direction, the band with a maximum at 2.95 eV with a large relative Stokes shift (SR = 0.56) in KBr crystal, characteristic for STE with a strongly asymmetric configuration, was detected. In crystals KI and KCl at deformation by 〈110〉 direction and in KBr crystal by 〈100〉 direction, no additional bands were detected besides to intrinsic σ-, π-luminescence. The appearance of an exciton with a strongly asymmetric configuration in KBr crystal is explained on the basis of the ratio of the radii of the anion and the cation, and also on the basis of the energy of excitons with different configurations on the surface of the adiabatic potential for the KI, KBr, and KCl crystals. For KBr crystal the ratio is 1.9, which is greater than in KI. The energy of the configuration transformations in KBr crystal is the smallest.