A 100-nsec isomer was found in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Po}$. The time-differential angular distribution of delayed $\gamma$ rays has been studied in the pulsed generation of aligned isomeric states in ($\alpha ,xn$) reactions with the use of cyclotron beam bursts. With a metallic lead target, no perturbation of the angular distribution during approximately 1 half-life could be detected. The $g$ factor of the isomeric state was determined to be $g=+0.88\mathrm{}\pm 0.05$, which suggests an interpretation of this isomer as the ${17/2}^{-}$ three-particle state of the [${\left(h_{\frac{9}{2}}\mathrm{}\right(p\left)\right)}^2{p}_{\frac{1}{2}}\mathrm{}\left(n\right)\mathrm{}$] configuration.

• Received 25 March 1968

DOI:https://doi.org/10.1103/PhysRev.175.1476