Electron-capture delayed fission properties of 244 Es

Electron-capture delayed fission was observed in 37-s ${}^{244}\mathrm{Es}$ produced via the ${}^{237}\mathrm{Np}{(}^{12}\mathrm{C}{,5n)}^{244}\mathrm{Es}$ reaction at 81 MeV (on target) with a production cross section of $0.31\ifmmode\pm\else\textpm\fi{}0.12\ensuremath{\mu}\mathrm{b}.$ The kinetic energies of coincident fission fragments were measured with our rotating wheel detection system and the average pre-neutron-emission total kinetic energy of the fragments was found to be $186\ifmmode\pm\else\textpm\fi{}19\mathrm{MeV}.$ The mass-yield distribution of the fission fragments is predominantly asymmetric. Based on the ratio of the number of fission events to the measured number of \ensuremath{\alpha} decays from the electron-capture daughter ${}^{244}\mathrm{Cf}$ (100% \ensuremath{\alpha} branch), the probability of delayed fission was determined to be $(1.2\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}.$ This value for the delayed fission probability fits the experimentally observed trend of increasing delayed fission probability with increasing Q value for electron capture.