Development of an Odd-$Z$-Projectile Reaction for Heavy Element Synthesis: ${}^{208}\mathrm{P}\mathrm{b}({}^{64}\mathrm{N}\mathrm{i},n){}^{271}\mathrm{D}\mathrm{s}$ and ${}^{208}\mathrm{P}\mathrm{b}({}^{65}\mathrm{C}\mathrm{u},n){}^{272}111$

Seven ${}^{271}\mathrm{D}\mathrm{s}$ decay chains were identified in the bombardment of ${}^{208}\mathrm{P}\mathrm{b}$ targets with 311.5 and 314.3 MeV ${}^{64}\mathrm{N}\mathrm{i}$ projectiles using the Berkeley Gas-filled Separator. These data, combined with previous results, provide an excitation function for this reaction. From these results, an optimum energy of 321 MeV was estimated for the production of ${}^{272}111$ in the new reaction ${}^{208}\mathrm{P}\mathrm{b}({}^{65}\mathrm{C}\mathrm{u},n)$. One decay chain was observed, resulting in a cross section of ${1.7}_{-1.4}^{+3.9}\mathrm{p}\mathrm{b}$. This experiment confirms the discovery of element 111 by the Darmstadt Group who used the ${}^{209}\mathrm{B}\mathrm{i}({}^{64}\mathrm{N}\mathrm{i},n){}^{272}111$ reaction.

Figure 1

Decay chains observed in the (a) ${}^{208}\mathrm{P}\mathrm{b}({}^{64}\mathrm{N}\mathrm{i},n){}^{271}\mathrm{D}\mathrm{s}$ and (b) ${}^{208}\mathrm{P}\mathrm{b}({}^{65}\mathrm{C}\mathrm{u},n){}^{272}111$ reactions. An implantation event is shown above each chain. The notation $x+y=z$ indicates that strip and upstream detector signals were observed simultaneously with energies $x$ and $y$, respectively, and sum $z$ (all in keV). The black triangle in the lower right corner of a box indicates the beam was shut off. Events with energies and positions estimated from one available strip signal only are denoted by ¶. A lifetime marked with a diamond (◆) is the sum of ${}^{271}\mathrm{D}\mathrm{s}$ and ${}^{267}\mathrm{H}\mathrm{s}$ lifetimes.