Production cross section and decay study of ${}^{243}$Es and ${}^{249}$Md

Abstract

In the study of the odd-$Z$, even-$N$ nuclei ${}^{243}$Es and ${}^{249}$Md, performed at the University of Jyväskylä, 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 $\hat{I}\pm$ 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 $\hat{I}\pm$ 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.