Spectroscopic features of dimer and dangling bond E' centres in amorphous silica

We performed first-principle embedded cluster calculations of the hyperfine parameters, g-tensors and optical excitation energies for the dimer and back-projected configurations of the E' centre in amorphous silica. The optical transition energies of these defects are calculated for the first time. We predict a strong optical transition at about 6.3 eV for the dimer configuration and a relatively weak transition at 5.6 eV for the back-projected configuration of the E' centre. These predictions could be used for further experimental identification of these centres. Our results support the dimer model of the E'δ centre, and for the first time provide a full range of spectroscopic parameters for the back-projected configuration of the E' centre in amorphous silica