O--LI-ZN CENTERS IN LI-DOPED ZNWO4 SINGLE-CRYSTALS CHARACTERIZED BY ESR AND ENDOR SPECTROSCOPY

In ZnWO4:Li single crystal a hole-type defect attributed to an O- ion has been observed by ESR and ENDOR spectroscopy after X-irradiation at 77 K. ENDOR results prove that this O- ion is associated with a nearb y Li ion and therefore the center is denoted as the O--Li-Zn center. T his defect is a lower symmetry version of the [Li]O center known in si mple oxides. The close relationship of the principal values and eigenv ectors of the (g) over tilde tensor of the O--Li-Zn center to those of previously reported hole centers in ZnWO4 supports the models of thos e centers as well. (C) 1998 Elsevier Science Ltd.