Electron spin resonance methods were used to study a new Sn-perturbed W5+ centre, with C1 symmetry, which was produced in single crystals that had been illuminated with 365nm ultra-violet light at 77K. The new centre was electron-like, with its highest spin density at a W site; but also with a substantial spin density at Sn which replaced a neighbouring Zn cation. It was denoted as being a W5+-SnZn4+ centre. The concentration of this defect was estimated to be less than 10-6.

Impurity Sn-Related Paramagnetic Defects in UV-Illuminated ZnWO4 Single Crystals. A.Watterich, L.A.Kappers, O.R.Gilliam: Journal of Physics - Condensed Matter, 1999, 11[5], 1333-40