Optical Absorption and Electron Paramagnetic Resonance of the E'-alpha   Center in Amorphous Silicon Dioxide
  We report a combined study by optical absorption (OA) and electron paramagnetic resonance (EPR) spectroscopy on the E'-alpha point defect in amorphous silicon dioxide (a-SiO2). This defect has been studied in beta-ray irradiated and thermally treated oxygen-deficient a-SiO2 materials. Our results have pointed out that the E'-alpha center is responsible for an OA Gaussian band peaked at 5.8 eV and having a full width at half maximum (FWHM) of 0.6 eV. The estimated oscillator strength of the related electronic transition is 0.14. Furthermore, we have found that this OA band is quite similar to that of the E'-gamma center induced in the same materials, indicating that the related electronic transitions involve states highly localized on a structure common to both defects. 
G. Buscarino, R. Boscaino, S. Agnello, and F. M. Gelardi