Recent studies of the hot fusion reaction ${}^{248}\mathrm{Cm}$(${}^{26}\mathrm{Mg}$,$\mathit{xn}$)${}^{274\text{−}x}\mathrm{Hs}$ have provided new nuclear decay data on ${}^{265,266}\mathrm{Sg}$ and confirmed the existence of an isomeric state in ${}^{261}\mathrm{Rf}$. The results reported in [J. Dvorak et al., Phys. Rev. Lett. 100, 132503 (2008)] suggest that all decay chains observed in previous studies of the reaction ${}^{248}\mathrm{Cm}$(${}^{22}\mathrm{Ne}$,$\mathit{xn}$)${}^{270\text{−}x}\mathrm{Sg}$, which were originally attributed to ${}^{266}\mathrm{Sg}$, originated from ${}^{265}\mathrm{Sg}$. Here, the decay properties of ${}^{265}\mathrm{Sg}$ are reevaluated. Indications for the existence of an isomeric state in ${}^{265}\mathrm{Sg}$ are found. The half-lives and main $\alpha$ particle energies of the two ${}^{265}\mathrm{Sg}$ states are 8.9 s/8.85 MeV and 16.2 s/8.70 MeV, respectively. Direct production of this isotope as an evaporation residue of a nuclear fusion reaction populates both states with similar intensity while $\alpha$ decay of ${}^{269}\mathrm{Hs}$ into ${}^{265}\mathrm{Sg}$ preferentially populates the longer-lived state, which in turn decays almost exclusively into the short-lived state in ${}^{261}\mathrm{Rf}$. The cross section of the reaction ${}^{248}\mathrm{Cm}$(${}^{22}\mathrm{Ne}$,$5n$)${}^{265}\mathrm{Sg}$ is reanalyzed and found to be of the order of a few hundred pb, assuming that $\alpha$ decay is the only decay mode of ${}^{265}\mathrm{Sg}$. A decay scheme that is consistent with the published data on ${}^{265}\mathrm{Sg}$ and ${}^{261}\mathrm{Rf}$ is proposed, which can serve as a working hypothesis in the design of new experiments dedicated to study the production and decay of these two isotopes.

• Received 20 March 2008

DOI:https://doi.org/10.1103/PhysRevC.77.064320