Effect of Low-Temperature Deformation on the Ex Luminescence of KI Single Crystals

Abstract

Simultaneous enhancement of the π- and σ-emissions of self-trapped excitons as well as the so-called E x-luminescence (maxima at ∼3.30, 4.15 and 3.04 eV, respectively) has been revealed in the X-ray luminescence spectra of KI single crystals additionally exposed to elastic uniaxial stress at 90 K. The intensity of all these luminescence bands linearly increases with relative degree of deformation up to ε = 1.0%, while the emissions undergo saturation at higher ε values (above elasticity limit). The similarity of the I = f(ε) dependences for intrinsic luminescence of self-trapped excitons and the E x emission allows to consider the latter also as the luminescence of intrinsic nature, tentatively connected with the radiative decay of self-trapping anion excitons with rather different configuration (with respect to these responsible for the π and σ components).