A detailed study of the 4.75 eV luminescence band of stishovite single crystal (SiO 2 with rutile structure) is reported. Kinetics of luminescence intensity is studied at durable (tens of minutes) X-ray excitation. The observed behaviour of the band intensity is explained by creation and destruction of luminescence centres depending on temperature both being determined by radiation stimulated diffusion of atomic particles. The luminescence decay is observed to last for minutes after X-ray irradiation while only for ns and hundreds of µs under pulsed e-beam irradiation suggesting a complicated recombination of the created defects. The UV band of stishovite is compared with the 4.9 eV luminescence band in α-quartz, which could not be created by X-ray. The latter being associated with transient centres created by destructive electronbeam irradiation or with permanent centres at neutron or γ-irradiation, and with oxygen-deficient luminescence of silica glass.

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I n Mg-and Ca-doped cc-Al,O, crystals irradiated by X-rays a t 80 K new paramagnetic colour centres are observed having an absorption band a t about 255 nm and an emission band a t 310 nm. The hyperfine structure of the EPR spectrum indicates that the unpaired electron spin interacts mainly with two AlZ7 nuclei. The optical and EPR spectra are consistent with the model of a centre involving one electron trapped a t an anion vacancy adjoining the substitutional divalent ion ( F~Q or Fc,). The luminescence band a t 290 nm observed in the TSL peak a t 225 K is suggested to result from the recombination of the holes with the FM~(Fc,) centres.