THE EFFECT OF THE RELAXATION OF 4D I- HOLE ON THE FORMATION OF EMISSION CENTERS IN ALKALI-HALIDES

The time-resolved luminescence spectra for KI, RbI and CsI were measur ed using VUV and X-ray synchrotron radiation. The emission band of fas t intrinsic luminescence (FIL) was observed for all these crystals. Th e position of FIL band is red-shifted (similar to 0.1 eV) relative to the sigma-exciton band. This type of emission is showed up at the temp eratures 80 to 300 K when the exciton emission was quenched and had a nonexponential decay characterised by times 0.1 and 10 ns. The FIL in CsI has the highest yield. The onset of CsI FIL excitation was shown t o be at photon energies higher than 20 eV. FIL yield exponentially inc reases with photon energies up to the energy of 4 d iodine core level (similar to 50 eV). The relaxation of 4d I- hole resulting in the doub le ionisation of the iodine ion may play an essential role in the crea tion of emission centers.