Delocalized Nature of the E’_delta Center in Amorphous Silicon Dioxide

We report an experimental study by electron paramagnetic resonance (EPR) of E'_delta point defect induced by gamma-ray irradiation in amorphous SiO2. 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 29Si (I = 1/2) nucleus. Moreover, determining the intensity ratio between this hyperfine doublet and the main resonance line of E'_delta center, we pointed out that the unpaired electron wave function of this center is actually delocalized over four nearly equivalent silicon atoms.