Nuclear Magnetic Moment ofBi207and Reorientation in the 0.8-sec Isomer ofPb207

The ground-state nuclear magnetic moment of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Bi}$ has been measured by nuclear orientation in the hyperfine field of a nickel host. The unperturbed anisotropy of the 1770-keV $\gamma$ ray gives the results $\mu =(4.63\mathrm{}\pm 0.25){\mu }_N$ and ${\left[\delta \right(\frac{E2\mathrm{}}{M1\mathrm{}}\left)\right]}_{1770}=-0.0836\mathrm{}\pm 0.0030$. Strongly attenuated anisotropies are observed for $\gamma$-ray transitions which pass through the 0.8-sec isomer in ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$, and these are quantitatively explained in terms of a perturbing quadrupole interaction in this state.