The level structure of ${}^{219}\mathrm{Rn}$ has been studied using the alpha decay of ${}^{223}\mathrm{Ra}$ and coincident gamma rays. While only modest changes are required in the level structure, and only above 342.8 keV, severe changes are required throughout the level scheme in the spin assigments. These changes allow the assignment of two sets of anomalous bands with ${K=5/2\mathrm{}}^{\pm }$ and ${K=3/2\mathrm{}}^{\pm }.$ The ${K=5/2\mathrm{}}^{\pm }$ bands have configurations intermediate between the reflection asymmetric configuration and the $g_{9/2}$ shell model configuration, while the ${K=3/2\mathrm{}}^{\pm }$ bands have configurations intermediate between the mixed reflection asymmetric configuration and the $i_{11/2}$ shell model configuration. Comparison of the systematics of ${}^{219}\mathrm{Rn}$ with neighboring isotones, isobars, and isotopes shows clearly the collapse of the quadrupole-octupole-type configurations into the less degenerate shell model configurations.

• Received 6 May 1997

DOI:https://doi.org/10.1103/PhysRevC.57.104