INFLUENCE OF UNIAXIAL DEFORMATION ON THE STRUCTURE OF SELF-TRAPPED EXCITONS IN ALKALI HALIDE CRYSTALS
By using luminescence spectroscopy, we have established the influence of low-temperature uniaxial deformation on the configuration of a self-trapped exciton (STE) in alkali halides crystals (AHС) at the instant of radiative relaxation. In face-centered crystals, there occurs the redistribution of the luminescence intensity from the asymmetric configuration of STE to the symmetric one (III→II→I-types), whereas in volume-centered crystals, on the contrary, the evidence counts in favour of the asymmetric configuration of STE (I→II-types). The external deformation in the <100> direction leads to an effective sliding of anions in the <110> direction that coincides with the direction of the STE squeeze which classically makes for the creation, of the symmetric STE configuration in the <110> direction, acting perpendicularly to the STE' length results in their stretching, which in turn brings into the creation of the asymmetric STE configuration with a higher degree of the polarization.