Defects in hydrogenated SrO

The paramagnetic $V_{\mathrm{OH}}$ and $V_{\mathrm{F}}$ defects generated by $\gamma$ irradiation at 77 K have been observed in hydrogenated SrO crystals. These defects are not stable at room temperature. EPR and electron-nuclear double-resonance measurements have been performed at low temperature in order to identify the impurity nucleus. In both cases, the defect is axially symmetric about a crystalline axis. An analysis of the anisotropic hyperfine coupling constants of these centers in MgO, CaO, and SrO shows that there is an approximate linear dependence between the distance from the trapped hole (oxygen-fluorine for the $V_{\mathrm{F}}$ and oxygen-oxygen for the $V_{\mathrm{OH}}$ and the crystal lattice parameter. A complex structure in the vicinity of $g\approx 2$, probably due to aggregate defects, is shown to be associated with hydrogen.