RELAXATION OF EXCITONS IN WIDE-GAP CSCL CRYSTALS

Optical characteristics of free and self-trapped excitons are investig ated in simple cubic CsCl crystals of high purity. The reflection, pho toluminescence, cathodoluminescence and x-ray luminescence spectra, as well as the excitation spectra for intrinsic, impurity and near-defec t emissions and spectra of the anion Frenkel defect creation by radiat ion are measured in CsCl crystals at 5-80 K in the spectral region of 2 to 10 eV. A weak emission at 8.3 eV and pi-emission of self-trapped excitons (2.82 eV) are detected in CsCl at 5 K. The energy gap is esti mated as E(g) = 8.4 eV at 5 K. Some peculiarities of the radiative and non-radiative decay of excitons in sc CsCl in comparison with those o f FCC KCl and RbCl crystals are discussed.