It was found that irradiated OH--doped crystals, at -30C, exhibited a new center which absorbed in the region of the Fz center at 380nm. The kinetics of defect formation and annihilation suggested that both OH- and Mg2+ had to be present in the host in order to permit the creation of the defect. A similarity between the excitation spectra of the present center, and the absorption of H2O centers in alkali chloride and bromide crystals, suggested that it must also be a so-called wet Fz center; but one which was more stable, due to the effects of Mg2+.

L.C.Courrol, L.Gomes: Journal of the Physics and Chemistry of Solids, 1997, 58[2], 281-6