On the decay properties of the neutron-deficient isotope 242Es

Abstract

The radioactive decay properties of ${}^{242}$Es were studied with significantly improved statistics compared to available literature data. This isotope was produced in the 3n evaporation channel of the fusion reaction of ${}^{48}$Ca+${}^{197}$Au. A half-life of 16.9(8)~s was deduced from 662 $\hat{I}\pm$ decays of ${}^{242}$Es, resulting in an $\hat{I}\pm$-decay branching of 41(3)\%. Twenty-six fission events with a half-life of 18.2${}_{-3.0}^{+4.5}$~s were assigned to originate from the electron-capture delayed fission of ${}^{242}$Es. The probability for the electron-capture delayed fission was measured to be 0.015(4), which improves and resolves ambiguities in available experimental data. We discuss all known cases for electron-capture delayed fission in Es, Bk, and Am isotopes and compare experimental data with predictions from a recent semi-empirical model. A cross section of 27(3)~nb was measured for the production of ${}^{242}$Es.