Repolarization of Negative Muons by Polarized $^{209}$Bi Nuclei
  A large $\mu^-$ polarization was achieved in muonic Bi atoms with the help of the strong hyperfine field in a polarized nuclear target. Using $^{209}$Bi nuclei polarized to ($59\pm9$)% in ferromagnetic BiMn, we observed a $\mu$-$e$ decay asymmetry of ($13.1\pm3.9$)%, which gives $\mu^-$ polarization per nuclear polarization equal to $-1.07\pm 0.35$. This value is almost consistent with $-0.792$ calculated for nuclei with spin $I= \frac{9}{2}$ and a positive magnetic moment under the assumption that the hyperfine interaction becomes effective in the lowest muonic states. 
R. Kadono, J. Imazato, T. Ishikawa, K. Nishiyama, K. Nagamine, T.   Yamazaki, A. Bosshard, M. D\"obeli, L. van Elmbt, M. Sch...
nucl-ex