Delayed fission from the electron-capture decay of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ was studied. The ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$(α,9n${)}^{232}$Am reaction with multiple ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$ targets was used to produce ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$. The fission properties and half-life of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ were measured using a rotating-wheel system. The half-life of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ was found to be 1.31±0.04 min from measurements of the fission activity. A highly asymmetric mass-yield distribution was observed for the fission activity, and the average total kinetic energy of the fission fragments was found to be 174±5 MeV. Radiochemical separations confirmed the elemental assignment of the fissioning species to americium or fission following shortly after the decay of americium. The cross section for ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ produced by this reaction and decaying by electron capture was determined to be 1.3±0.2 μb by measuring the intensities of the daughter plutonium K x rays in radiochemically separated americium samples. The delayed-fission probability was found to be (6.9±1.0)×${10}^{\mathrm{-}4}$ from the measured ratio of fissions to plutonium K x rays. The observed fissions were unambiguously assigned to electron-capture-delayed fission of americium by measuring the time correlation between the plutonium K x rays resulting from americium K capture and the subsequent fission.

• Received 3 April 1990

DOI:https://doi.org/10.1103/PhysRevC.42.1480