The enhancement of exciton-like luminescence in KCl single crystals under local and uniaxial elastic lattice deformation

Radiative annihilation of exciton-like formations (bound excitons) in KCl single crystals doped with various impurity cations (Li, Na, Sr) has been studied using highly sensitive luminescence methods. In KCl:Na with different sodium concentration, X-ray luminescence bands with the maxima at 2.8 and 3.1 eV, which and attributed to exciton-like formations in the region of local lattice deformation by single Na+ and pair Na+-Na+ centers, become significantly more intense with sodium impurity concentration. The luminescence efficiency of such bound anion excitons also increases in the KCl:Na crystals exposed to a uniaxial elastic stress along the 〈100〉 and 〈110〉 crystallographic directions. The influence of temperature as well as lattice symmetry lowering due to applied elastic deformation (external action) or local deformation in the vicinity of impurity ions (internal action) on the efficiency of the recombination formation of bound excitons has been analyzed.