Recently, the interest to investigations of the systems that are capable to change a spin condition of charge carriers has been increased. These systems have been used as media for quantum computers. In the present paper a circular polarization photoluminescence of the defects in SiO₂ has been investigated. A circular polarization degree is a sensitive indicator of a spin state of the charge carriers. Grown at the room temperature 0.5 mm SiO₂ was irradiated with electrons. The dose of irradiation was 0.3 K/cm². An Ar⁺ laser (λ = 488 nm) with a power of 14 mW was used for photoluminescence excitation. The circular polarization photoluminescence spectra were recorded using quarter-wave plate and Glan prism. The measurements were carried out at the room temperature. In the photoluminescence spectrum of the investigated samples a wide band with a maximum at ~650 nm was observed. The origin of this band was associated with a non-bridging oxygen atom (-Si-O^.). A circular polarization degree was calculated as P=(I₊ - I_-)/(I₊ + I_-), where I₊ and I_- are the intensities of a clockwise polarized and a counterclockwise polarized photoluminescence, correspondingly. The circular polarization degree equals to 3.8%. We also have investigated the circular polarization photoluminescence of the silicon nanocrystalls in SiO₂. But these measurements have not given a beneficial effect. The spin relaxation time was calculated and equaled to 2.24 microseconds. The mechanism of this effect is discussed.
The work was supported in part by the Russian Foundation for Basic Research (grant no.02-02-17719).

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