ESR study of a new electron center in synthetic stishovite, a high-pressure polymorph of silica

A new unidentified electron center in gamma-ray-irradiated synthetic stisho vite, a high-pressure polymorph of SiO2, was detected by X-band electron sp in resonance. It has an anisotropic g-factor of orthorhombic symmetry, g(1) = 1.9764, g(2) = 1.9527 and g(3) = 1.9370. The signal intensity was satura ted at a microwave power of 2 mW. Annealing experiments show that the cente r was annealed out around 280 K and unstable at room temperature. The cente r may be ascribed to a titanium electron center on the basis of a relativel y large g-shift and a comparison with the paramagnetic centers in quartz.