THE E'(DELTA) AND TRIPLET-STATE CENTERS IN X-IRRADIATED HIGH-PURITY AMORPHOUS SIO2

High-purity silicas synthesized by the chemical-vapor-deposited soot r emelting method were studied by electron-spin-resonance techniques aft er being irradiated by x rays at 77 K or higher temperatures. The spec tra or the E(delta) center including its Si-29 hyperfine splitting, an d the tripler-state center, were measured using two different detectio n modes. The effects of x-ray dose, thermal annealing, hydrogen treatm ent, and impurities were examined; the E and the triplet-slate centers have a similar dependence on all these parameters, indicating that th ey share a common precursor. These centers an found only in low OH, ox ygen-deficient samples, There appears to be no correlation with chlori ne impurities. The measured intensity of the E(delta)' center's Si-29 hyperfine signal indicates that approximately four Si atoms are involv ed. A model for this center and the triplet-state center is proposed. (C) 1996 American Institute of Physics.