The level scheme of ${}^{212}\mathrm{Rn}$ has recently been expanded and extended to spins of $~39\hslash$ and excitation energies of about 13 MeV using the ${}^{204}\mathrm{Hg}$(${}^{13}\mathrm{C}$,$5n$)${}^{212}\mathrm{Rn}$ reaction and $\gamma$-ray spectroscopy. Time-correlated techniques were used to obtain channel selectivity and improved sensitivity. New $\gamma$-ray branches from states associated with valence proton configurations as well as a number of new states below the ${22}^{+}$ isomer have been identified. The excitation energy of the ${22}^{+}$ core excited isomer itself has been established through the observation of several branches parallel to the main decay, implying a transition energy of $7.6$ keV for the previously unobserved decay to the ${20}_2^{+}$ state. The level scheme above the ${22}^{+}$ isomer includes two new isomers with $\tau =25(2)$ ns and $\tau =12(2)$ ns placed at $12,211$ and $12,548$ keV, respectively. These are attributed to configurations involving triple neutron core excitations coupled to the aligned valence protons. The results are compared to semiempirical shell-model calculations, which can account for many of the states observed, with considerable precision for the valence proton configurations but with significant energy discrepancies for some core excited configurations. Calculations within the deformed independent particle model (DIPM) have also been carried out for the main core excited configurations at high spin and compared with both experiment and the empirical shell-model approach. The possible sources of discrepancies in both approaches are discussed, and it is suggested that anomalously low excitation energies are predicted for specific configurations in the DIPM.

• Received 22 July 2009

DOI:https://doi.org/10.1103/PhysRevC.80.054320