Further characterization of theE1′center in crystalline SiO2

Electron-spin resonance (ESR) is used to investigate the formation and thermal anneal characteristics of $E_1^{\prime }$ centers in high-quality synthetic quartz. These centers are produced by ionizing radiation near room temperature followed by annealing to 300°C. The resulting concentration depends on the specific irradiation temperature, the nature of previous irradiation and thermal anneals, and whether the sample is air swept or unswept. Migration of interstitial alkali ions (${\mathrm{Li}}^{+}$ and/or ${\mathrm{Na}}^{+}$) as a result of irradiation correlates with the production of the $E_1^{\prime }$ centers, and a relationship between the ${\left[\mathrm{A}\mathrm{l}{\mathrm{O}}_4\right]}^0$-center concentration and the $E_1^{\prime }$-center concentration is also observed. Electron-nuclear double resonance is used to show that the two "weak" hyperfine interactions (8- and 9-G splittings) are with ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ nuclei. From the angular dependence of the ESR data taken at 300 K, complete sets of spin-Hamiltonian parameters are determined for the $\overleftrightarrow{g}$ matrix and the three ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine (one strong and two weak) matrices.