Optical absorption methods were used to study the thermal annihilation of O vacancies in thermochemically reduced crystals. It was found that the annihilation behavior was sample-dependent, and varied markedly; depending upon the F-center concentration.

Dynamics of F-Center Annihilation in Thermochemically Reduced MgO Single Crystals. A.I.Popov, M.A.Monge, R.Gonzalez, Y.Chen, E.A.Kotomin: Solid State Communications, 2001, 118[3], 163-7