Production cross section and decay study of 243Es and 249Md

Abstract

In the study of the odd-Z, even-N nuclei 243Es and 249Md, performed at the University of Jyväskylä, the fusion-evaporation reactions 197Au(48Ca,2n)243Es and 203Tl(48Ca,2n)249Md have been used for the first time. Fusion-evaporation residues were selected and detected using a gas-filled separator coupled with its focal-plane spectrometer. For 243Es, the recoil decay correlation analysis yielded a half-life of 24±3s and a maximum production cross section of 37±10nb. In the same way, a half-life of 26±1s, an α-branching ratio of 75±5%, and a maximum production cross section of 300±80nb were determined for 249Md. The decay properties of 245Es, the daughter of 249Md, were also measured: an α-branching ratio of 54±7% and a half-life of 65±6s. Experimental cross sections were compared to the results of calculations performed using the kewpie2 statistical fusion-evaporation code.