In Li-doped single crystals, a hole-type defect which was attributed to an O- ion was observed, using electron spin resonance and electron nuclear double resonance spectroscopic techniques, after X-irradiation at 77K. The electron nuclear double resonance results proved that this O- ion associated with a nearby Li ion, to give an O--LiZn center. This defect was concluded to be a lower-symmetry version of the [Li]0 center which was found in simple oxides.

A.Watterich, A.Hofstaetter: Solid State Communications, 1998, 105[6], 357-62