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  direction leads to an effective sliding of anions in the  direction that coincides with the direction of the STE squeeze which classically makes for the creation, of the symmetric STE configuration in the  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.