10-K EPR OF AN OXYGEN-HOLE ALUMINUM CENTER, [ALO4](0), IN X-IRRADIATED ZIRCON, ZRSIO4

Precise parameter interaction matrix determinations, including Al-27 hyperfine and nuclear electric quadrupole matrices, are reported for an aluminium centre, with an electron removed from an adjacent oxygen and referred to as an oxygen-hole centre, in x-irradiated zircon based on 8.9 GHz EPR measurements at around 10 K. Each of the parameter interaction matrices exhibits monoclinic symmetry indicating sites of Laue class 2/m for both the hole-centre and the interacting Al-27 nucleus. Consideration of earlier reported results for two single electron-hole centres in zircon, and comparison with results for a similar centre in a quartz, show that the hole-centre is trapped at a short bonded ligand O in the zircon structure and interacts with an aluminium nucleus replacing Si at an adjacent site; each of the O and Si sites of the zircon structure have point group symmetry m.