ENDOR investigation of the F⁺ centre in Mg¹⁷O

ESR and ENDOR have been used to investigate the F⁺ centre in MgO crystals enriched in the isotope ¹⁷O. A study has been made of the hyperfine interactions between the trapped electron and ¹⁷O nuclei at the first four anion shells neighbouring the oxygen vacancy. The results are consistent with a wavefunction in which most of the unpaired spin is in 2p orbits on the twelve nearest O^2- ions with smaller admixtures of 3s and 3p orbitals in the six nearest Mg²⁺ ions. There is also evidence for small 2p admixtures at further O^2- sites.