In the study of the odd-$Z$, even-$N$ nuclei $^{ 243}$Es and $^{ 249}$Md, performed at the University of Jyv\"askyl\"a, the fusion-evaporation reactions $^{ 197}$Au($^{ 48}$Ca,2$n$)$^{ 243}$Es and $^{ 203}$Tl($^{ 48}$Ca,2$n$)$^{ 249}$Md have been used for the first time. Fusion-evaporation residues were selected and detected using the RITU gas-filled separator coupled with the focal-plane spectrometer GREAT. For $^{ 243}$Es, the recoil decay correlation analysis yielded a half-life of $24 \pm 3$s, and a maximum production cross section of $37 \pm 10$ nb. In the same way, a half-life of $26 \pm 1$ s, an $\alpha$ branching ratio of 75 $\pm$ 5%, and a maximum production cross section of 300 $\pm$ 80 nb were determined for $^{ 249}$Md. The decay properties of $^{ 245}$Es, the daughter of $^{ 249}$Md, were also measured: an $\alpha$ branching ratio of 54 $\pm$ 7% and a half-life of 65 $\pm$ 6 s. Experimental cross sections were compared to the results of calculations performed using the KEWPIE2 statistical fusion-evaporation code.
Categories: nucl-ex