Possible evidence of a copper-related electron paramagnetic resonance centre in diamond

The EPR centre W36, found in natural type IIb diamond, has been previously attributed to a boron-related point defect, largely on account of its four line hyperfine structure attributed to B-11. The attribution has been re-examined, and no simple boron-related site has been found capable of accounting for the measured parameters. It is concluded that W36 is much more likely to be related to copper, probably at a semi-vacancy site (C3VCuVC3)(+). An unusual feature of this centre is the very small value of the fine structure parameter D. Two other centres, W10 and W32, with similarly small values of D, which may also be associated with 3d ions, are briefly discussed.