Excited states in ${}^{209}\mathrm{Fr}$ have been studied using the ${}^{197}\mathrm{Au}({}^{16}\mathrm{O},4n){}^{209}\mathrm{Fr}$ reaction with pulsed beams and $\gamma$-ray and electron spectroscopy. A comprehensive scheme has been established up to an excitation energy of about 6 MeV and spins of about $49/2\hslash$. Several isomers have been identified including a $J^{\pi }=25/2^{+}$, $\tau =48(3)$ ns state at 2130 keV and a $606(26)$ ns, $45/2^{-}$ state at 4660 keV. The latter state decays via an enhanced $E3$ transition with a strength of 28.8(12) W.u. It can be identified with a similar isomer in the heavier odd isotopes ${}^{211}\mathrm{Fr}$ and ${}^{213}\mathrm{Fr}$, arising from the maximal coupling of the five valence protons in the $\pi h_{9/2}^3{i}_{13/2}^2$ configuration. The systematics of the yrast states in the odd-$A$ isotopes are discussed, including the presence of states arising from the main proton configurations coupled to the $p_{1/2}$, $f_{5/2}$, and $i_{13/2}$ neutron holes. Shell-model configurations are assigned to many of the observed states. The isotopic assignment differs from earlier work, which is shown to be erroneous.

• Received 5 March 2009

DOI:https://doi.org/10.1103/PhysRevC.79.054313