M e Centers

They dissociate the H2 molecule with a nonactivated reaction and an energy release, 0.5 eV, close to the measured one. 

The structure of the resulting MgO(H+)(H ) center is consistent with an heterolytic dissociation of H2 and the computed vibrations are in full agreement with the observation. 

The removal of a neutral H atom from the MgO(H+)(H ) center has a cost consistent with the use of UV light for the process and results in a trapped electron at the MgO surface, MgO(H+)(e )trapped- 

The computed transition energies for the trapped electron, about 2eV, are close to values reported for optical excitations at the surface of polycrystalline MgO where Fg(H)+ defect centers have been created according to reactions (2.6) and (2.7). 

Similar centers can be formed by alkali and other adsorbed atoms M, which can donate electrons to the surface and stabilize them by the Coulomb field created by the corresponding M+ cation [186]. The centers illustrated 

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