Nuclear Magnetic Moment of the 158-kev52-State ofHg199

The nuclear magnetic moment of the 158-kev, ${\frac{5}{2}}^{-}$ state has been measured by precessing, in a solid gold environment, the ${\frac{3}{2}}^{-}$ (334 kev) ${\frac{5}{2}}^{-}$ (158 kev) ${\mathrm{½}}^{-}$ gamma ray-gamma ray angular correlation in an external magnetic field of 26 000 gauss. The value obtained, ${\mu }_{\frac{5}{2}}=+1.03\mathrm{}\pm 0.08$ nm, includes a 5% correction for quadrupole attenuation as determined by studying the angular correlation as a function of the delay of the intermediate state. The value is compared to the recent prediction of de-Shalit assuming that the ${\frac{5}{2}}^{-}$ state originates from the coupling of the ${\mathrm{½}}^{-}$ ground state (${\mu }_p=+0.504\mathrm{}$ nm) with the 2+ excitation of the core. The magnetic moment of the core excitation was obtained from the $M1\mathrm{}$ gamma-ray mean life of the 50-kev transition between the ${\frac{3}{2}}^{-}$ (208 kev) and ${\frac{5}{2}}^{-}$ (158 kev) core-particle doublet. That mean life, determined to be ${\tau }_{\gamma }\mathrm{}\left(50\right)=(4.46\mathrm{}\pm 1.0)\times {10}^{-9\mathrm{}}$ sec, leads to predicted magnetic moments of ${\mu }_{\mathrm{core}}=(+{{0.33}_{-0.25\mathrm{}}}^{+0.17\mathrm{}})$ mn and ${\mu }_{\frac{5}{2}}=(+{{0.84}_{-0.25\mathrm{}}}^{+0.17\mathrm{}})$ nm.