Electric quadrupole interactions of the short-lived β-emitter 12N in insulator crystals (12N implanted in single crystal TiO2)

The electronic structure of nitrogen atoms as impurities in an ionic TiO(2) crystal has been investigated by analyzing electric field gradients (EFGs) measured by use of short-lived beta-emitting (12)N implanted following nuclear reactions. Conventional beta-NMR and its modification, suitable for the detection of quadrupole effects in the NMR spectra, were used for the investigation of hyperfine interactions of (12)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 (12)N has been determined from the NMR detection of (12)N implanted in BN(hexagonal) crystal. Here the EFG at the N atom in BN was measured by detecting the FT-NMR of (14)N in the crystal. The EFGs in TiO(2) are compared with the theoretical predictions based on the nb initio band-structure calculation in the framework of the KKR method.