Optical transitions associated with γ -radiation-induced defects in crystalline α-quartz were investigated by photoluminescence excited by both pulsed synchrotron radiation and steady-state light. After a 10 MGy γ -dose we observed two emissions at 4.9 eV (ultraviolet band) and 2.7 eV (blue band) excitable in the range of the induced absorption band at 7.6 eV. These two luminescence bands show a different temperature dependence: the ultraviolet band becomes bright below 80 K; the blue band increases below 180 K, but drops down below 80 K. Both emissions decay in a timescale of a few ns under pulsed excitation, however the blue band could also be observed in slow recombination processes and it afterglows in about 100 s at the end of steady-state excitation. The origin of the observed luminescence bands and the comparison with optical features of oxygen-deficient centres in silica glass are discussed in the framework of different models proposed in the literature.

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The emission spectra and the excitation spectra of various emissions have been measured in LiF crystals at 9 K using VUV radiation of 10-33 eV. Contrary to the luminescence of selftrapped excitons (3.4 eV), the efficiency of several extrinsic emissions (4.2, 4.6 and 5.8 eV) is very low in the region of an exciton absorption (12.4-14.2 eV). A single exciting photon of 28-33 eV is able to create a primary electron-hole (e-h) pair and a secondary exciton. The tunnel phosphorescence has been detected after the irradiation of LiF by an electron beam or X-rays at 6 K, and several peaks of thermally stimulated luminescence (TSL) at 12-170 K appeared at the heating of the sample. It was confirmed that the TSL at 130-150 K is related to the diffusion of self-trapped holes (V K centres). The TSL peak at ~160 K is ascribed to the thermal ionisation of F′ centres. The TSL at 20-30 K and 50-65 K is caused by the diffusion of interstitial fluorine ions (I centres) or H interstitials, respectively. The TSL peak at ~13 K, the most intense after electron or X-irradiation, cannot be detected after LiF irradiation by VUV radiation, selectively forming excitons or e-h pairs. The creation of a spatially correlated anion exciton and an e-h pair is needed for the appearance of this peak: an exciton decays into an F-H pair, a hole forms a V K and an electron transforms H into I (an F-I-V K group is formed) or an F centre into a two-electron F′ centre (an F′-H-V K group). The analysis of the elementary components of the 9-16 K TSL showed that a phonon-induced radiative tunnel recombination of F′-V K (5.6 eV), F-H (~3 eV) and F-V K (3.4 eV) occurs within these groups.Short Title: Low-temperature excitonic, electron-hole and interstitial-vacancy processes in LiF

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The processes of the creation, stabilization and annealing of anion Frenkel defects have been investigated in MgO and MgO : Be single crystals irradiated by α particles, uranium swift ions or fast neutrons at 300 K and also additionally irradiated by 5 keV electrons at 6 K. Neutral oxygen interstitials undergo stabilization due to their association with the holes localized near Be 2+ ions or near cation vacancies. The peculiarities of the processes of nonimpact creation and stabilization of point defects under conditions of a high density of electronic excitations formed in the tracks of swift heavy ions have been considered by the example of MgO crystals, where the creation energy of a pair of long-lived Frenkel defects exceeds the energy gap, E FD > E g .