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BYTwo types of luminescent centres a r e created by high-temperature electrolysis of crystalline and glassy Si02 in silver electrodes. &+ is the nucleus of these centres /l/. A decreased Ag+ concentration was observed under X-ray irradiation of the samples /2/ and this leads to the creation of some luminescent centres. A centre giving rise to a luminescent band at 2.9 eV was observed in samples irradiated at liquid nitrogen temperature (LNT). The nature of this centre was studied in /2/ and it was shown that it corresponds to an Ago centre.Warming-up the samples irradiated at LNT to room temperature (RT) leads to the disappearance of the luminescent band at 2.9 eV and growth of a band at 2.3 eV, the nature of which is still unknown. On the other hand, the centre which gives the luminescent band at 2.3 eV may be created both by X-ray and ultraviolet irradiation in all Si0,-Ag samples at RT. The present work deals with the nature of this luminescent centre.The experimental technique has been described in previous work /1 to 4/.The excitation spectrum of the luminescence band at 2.3 eV contains bands at 3.0 eV and 3.9 to 4.1 eV which a r e observable in different samples both in crystals and in glasses. The bands in the region of 4.5 to 9 eV a r e different for different samples (Fig. 1). The

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