Luminescence quantum yield and multiplication of electronic excitations in the corundum crystals

The excitation spectra of luminescence in irradiated and nonirradiated corundum crystals are investigated by means of highly polarised synchrotron radiation in 5 to 30 eV region. In the fundamental absorption region the double-exciton peaks are observed in the region 8.5-9.2 eV for irradiated (especially by neutrons) crystals at temperature 90 K. At 9.5 eV sharp drops appeared, in the luminescence spectrum space which were interpreted as nonirradiative near-surface recombination, the probability of which sharply increased at high absorption coefficients. The enhancement of the luminescence efficiency in the high-energy region was connected with the decay effect of electron excitations as well as with the influence of volumetric excitations leading to the enhancement of recombination glow