TIME-RESOLVED PHOTOLUMINESCENCE OF ALPHA-CENTERS IN NEUTRON-IRRADIATED SIO2

Photoluminescence in various types of silica (a-SiO2) both unirradiate d and neutron irradiated has been studied in the range 10-300 K. The a lready reported alpha emissions at 4.25 eV and at 4.35 eV, whose respe ctive excitation bands peak at 5.10 eV and 4.96 eV, have been found to be excited also in a band peaking at approximately 7.6 eV; the temper ature dependence of their intensities has also been investigated for b oth, excitations. Time resolved emission spectroscopy excited by KrF e xcimer laser (5 eV) allowed the detection of the different lifetimes o f the two a emissions. Similar studies on neutron irradiated quartz (c -SiO2) have evidenced the presence of the center emitting at 4.35 eV u p to now observed only in a-SiO2.