Nuclear Magnetic Resonance of OrientedAu196,Au198, andAu200m

Thermal equilibrium nuclear orientation was employed to orient nuclei of ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{198}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{200m}{}_{}{}^{}\mathrm{Au}$ as dilute impurities in nickel and iron at temperatures down to 4 mK. The degree of nuclear orientation was determined from the anistropy of $\gamma$ radiation emitted from the oriented nuclei. For $\mathrm{N}\mathrm{i}\left({}_{}{}^{200m}{}_{}{}^{}\mathrm{Au}\right)$ both the magnetic hyperfine interaction $\left|\mu H\right|=(7.65\mathrm{}\pm 0.30)\times {10}^{-18\mathrm{}}$ erg and the magnetic hyperfine splitting $\left|\frac{\mu H}{I}\right|=(6.473\mathrm{}\pm 0.012)\times {10}^{-19\mathrm{}}$ erg were determined from an analysis of the temperature dependence of $\gamma$-ray anisotropies and by nuclear magnetic resonance on oriented nuclei (NMR/ON), respectively. As a result the spin $I$ and the magnetic moment $\mu$ of the isomeric state could be derived as $I^{\pi }={12}^{\mathrm{}(-)\mathrm{}}$ and $\mu \left({12}^{-}\right)=\{+\}\left\{\mathrm{}\right(-\left)\mathrm{}\right\}(6.10\mathrm{}\pm 0.20){\mu }_N$. From the measured anisotropies of five $\gamma$ rays originating from the ${\beta }^{-}$ decay of ${}_{}{}^{200m}{}_{}{}^{}\mathrm{Au}$, spins and multipolarities could be assigned in the ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$ decay scheme. Nuclear magnetic resonance was also observed on oriented ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{198}{}_{}{}^{}\mathrm{Au}$ in nickel at frequencies of 58.3±0.4 MHz and 58.5±0.4 MHz, respectively. The hyperfine interaction for Ni(${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$), measured previously by spin echo, and our result for Ni(${}_{}{}^{196,198}{}_{}{}^{}\mathrm{Au}$) agree with the known atomic hyperfine anomalies between ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{196,198}{}_{}{}^{}\mathrm{Au}$ only if the hyperfine field is assumed to have a noncontact contribution. For Ni(${}_{}{}^{196,198}{}_{}{}^{}\mathrm{Au}$) with $H_{\mathrm{hf}}=(-)260.8\pm 1.3$ kOe, the contact part is then found to be $H_{\mathrm{c}}=-367\mathrm{}\pm 70$ kOe, with the noncontact contribution amounting to $H_{\mathrm{nc}}=+106\mathrm{}\pm 70$ kOe. The angular distributions of several $\gamma$ rays are in excellent agreement with a decay scheme proposed by Cunnane et al., in which they found negative-parity levels of spins 5, 7, 9, and 11 at energies of 1852, 1963, 2144, and 2642 keV, respectively, in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$.