Electric Quadrupole Interactions of the Short-Lived ß-Emitter

The electronic structure of nitrogen atoms as impurities in an ionic T i0 2 crystal has been investigated by analyzing electric field gradients (EFGs) measured by use of short-lived /3-emitting N implanted following nuclear reactions. Conventional ß-NMR and its modification, suitable for the detection of quadrupole effects in the NMR spectra, were used for the investigation of hyperfine interactions of N located in substitutional sites of O atoms and interstitial sites in the crystal. In order to deduce absolute values of the EFGs from the obtained eqQ/h, the quadrupole moment of N has been determined from the NMR detection of N implanted in BN(hexagonal) crystal. Here the EFG at the N atom in BN was measured by detecting the FT-NMR of l 4 N in the crystal. The EFGs in T i0 2 are compared with the theoretical predictions based on the ab initio band-structure calculation in the framework of the KKR method.