We report on an attempt to produce and detect ${}^{268}\mathrm{Hs}$ and ${}^{269}\mathrm{Hs}$ in the nuclear fusion reaction ${}^{25}\mathrm{Mg}+{}^{248}\mathrm{Cm}$ using the gas phase chemistry apparatus COMPACT. No decay chains attributable to the decay of hassium isotopes were observed during the course of this experiment. From the nonobservation of ${}^{269}\mathrm{Hs}$ we derive a cross section limit of 0.4 pb (63% confidence limit) for the reaction ${}^{248}\mathrm{Cm}({}^{25}\mathrm{Mg},4n){}^{269}\mathrm{Hs}$ at a center-of-target beam energy of 140 MeV. The evaluated cross section limit for the ${}^{248}\mathrm{Cm}({}^{25}\mathrm{Mg},5n){}^{268}\mathrm{Hs}$ reaction depends on the assumed half-life of unknown ${}^{268}\mathrm{Hs}$. Current systematics of the half-lives for even-even Hs isotopes suggests a value of 0.5 s, resulting in a cross section limit of 1.3 pb.

• Received 3 December 2008

DOI:https://doi.org/10.1103/PhysRevC.79.037602