Electron paramagnetic resonance evidence of Ho at three chemically inequivalent sites in gamma irradiation SrSO4:UO22+

Electron Paramagnetic Resonance investigations of gamma irradiated SrSO4:UO22+ at low modulation amplitude have revealed the presence of three sites for H0 centre in the phosphor. The three sites were identified to be substitutional ones from their A-values. Of these, one was found to give isotropic spectrum, while the other two were found to be anisotropic. The three inequivalent sites possibly arise due to bonding of H0 centre with different sulphate anions such as SO4-, SO4- and SO3-. The observation of the anisotropic spectra suggests that there is a slight but varying extent of non-s character to the unpaired electron on the H0 centre brought about by differences in chemical bonding involving neutral hydrogen atoms. (author)