Effect of uniaxial strain on the structure of self-localized excitons in alkali halide crystals

We have used luminescence spectroscopy to establish the effect of low-temperature (100 K) elastic uniaxial strain on the configuration of a self-localized exciton (SLE) in alkali halide crystals (AHCs) at the instant of radiative relaxation. In face-centered (fc) alkali halide crystals, redistribution of the luminescence intensity occurs from the asymmetric SLE configuration to the symmetric SLE configuration (type III → II → I), while conversely in body-centered (bc) alkali halide crystals the redistribution occurs in favor of the asymmetric (polarized) SLE configuration (type I → II). External strain along the 〈100〉 direction leads to effective slip of the anions in the alkali halide crystals along the 〈110〉 direction, coinciding with the direction of compression of the SLE, which promotes creation of preferentially the symmetric SLE configuration, while strain along the 〈110〉 direction, acting perpendicularly to the length of the SLE, leads to elongation of the SLE, which promotes creation of the asymmetric SLE configuration with a higher degree of polarization. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 67–72, January–February, 2007.