Computed paramagnetic properties for an E′ center produced from the twofold coordinated Si or Ge in silica

This paper introduces a model of the E γ ′ center involving a twofold coordinated silicon or germanium atom as precursor. This one relaxes in its positively charged state through interaction with a neighboring oxygen atom forming a threefold coordinated silicon atom having characteristics of the well known E γ ′ center. By neutralizing the hole, we have observed that this relaxation is reversible without activation energy. The contribution of the central atom to the isotropic hyperfine coupling constant is found to be 44 mT in agreement with the experimental value: 42 mT.