Multi-frequency high-field EPR study of (H+)(e−) pairs localized at the surface of polycrystalline MgO

The g-tensor of excess electron centres (H+)(e−) generated at the surface of polycrystalline MgO has been determined by multi-frequency, high-field electron-paramagnetic resonance (EPR) performed at 9.5, 34, 190 and 285 GHz. The A tensor for the interacting 1H was also determined by complementary Q-band electron-nuclear double resonance (ENDOR). Due to the high spectral resolution the anisotropy of the g-tensor could be fully resolved in the powder continuous-wave EPR spectrum. Computer simulation of the experimental data revealed small g-tensor anisotropies: Δgx = −0.00294, Δgy = −0.00286, Δgz = −0.00101, with Δgi = gi − 2.0023.