29Si attribution of the 1.3 mT hyperfine structure of the E′γ centers in amorphous SiO2

We report an experimental investigation by electron paramagnetic resonance of the doublet of lines split by ∼1.3 mT and centered on the E′γ; center resonance line in the spectrum of irradiated amorphous SiO2 . Commercial and sol-gel materials, some of which subjected to hydrogen-deuterium exchange, were investigated. Exposure to γ or Β rays at room temperature of the samples and subsequent thermal treatments were carried out to induce the defects and to study their thermal stability. In all the materials used the ratio between the signal of the E′γ centers and that of the 1.3 mT doublet is constant and independent of the OH and OD contents. Furthermore, the 1.3 mT doublet and the E′γ center feature similar thermal stability. These results support the attribution of the 1.3 mT doublet to the hyperfine interaction between the unpaired electron magnetic moment of the E′γ center and the nuclear magnetic moment of a second near neighboring 29Si atom. Our results also suggest that the E′γ site needs an appropriate surrounding of 29Si in back-bond configuration to experience this hyperfine interaction. © 2009 American Institute of Physics.