We report an experimental study by electron paramagnetic resonance (EPR) of $E_{\delta }^{\prime }$ point defect induced by $\gamma$-ray irradiation in amorphous $\mathrm{Si}{\mathrm{O}}_2$. We obtained an estimation of the intensity of the 10 mT doublet characterizing the EPR spectrum of such a defect arising from hyperfine interaction of the unpaired electron with a ${}^{29}\mathrm{S}\mathrm{i}$ ($I=1/2$) nucleus. Moreover, determining the intensity ratio between this hyperfine doublet and the main resonance line of $E_{\delta }^{\prime }$ center, we pointed out that the unpaired electron wave function of this center is actually delocalized over four nearly equivalent silicon atoms.

• Received 10 December 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.125501