PARAMAGNETIC DEFECTS ASSOCIATED WITH HYDROGEN ADSORBED ON SURFACE OF MAGNESIUM AND CALCIUM OXIDES

The irradiation of MgO and CaO in the form of small particles (100-300Å) leads to the formation of surface paramagnetic centers (S centers) which will react with oxygen. Both S centers and new surface centers (SH centers) with g = 1.9998 are formed if the oxides are γ-irradiated in the presence of hydrogen or deuterium. The SH center shows a hyperfine coupling from one hydrogen nucleus, and both the S and SH centers show a hyperfine interaction with the Mg25 nuclei of the lattice to give splitting constants of 25.5 and 10.2 gauss, respectively. These surface centers are believed to be intrinsic defects consisting of an electron trapped at a surface anion vacancy and provide a surface equivalent of the well-known bulk defects (F centers). The nearby proton in the SH center suggests that the hydrogen must react with surface oxygen ions during irradiation. © 1968.