The isomer ${}_{}{}^{207}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$ was produced via the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},4n)$ reaction and also by bombardment of natural Hg targets with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions. The isomer with a half-life of 181 ± 18 μs was found to decay by a cascade of two transitions 234 keV ($M2\mathrm{}$) and 665.1 keV ($E2\mathrm{}$) to the Rn ground state and was assigned as an $i_{\frac{13}{2}}$ shell-model state.

NUCLEAR REACTIONS ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}({}_{}{}^{14}{}_{}{}^{}\mathrm{N},4n)$, $E=70\mathrm{}-120$ MeV; nat $\mathrm{Hg}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},5\mathrm{}-7n)$, $E=126\mathrm{}$ MeV. RADIOACTIVITY ${}_{}{}^{207}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$; measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $I_{\gamma }$, $\gamma K\mathrm{x}$ coin; ${}_{}{}^{207}{}_{}{}^{}\mathrm{Rn}_{}^m{}_{}{}^{}$ deduced multipolarities, levels, $J$, $\pi$.

• Received 13 February 1974

DOI:https://doi.org/10.1103/PhysRevC.10.766