The new plutonium isotope, ${}^{231}\mathrm{Pu},$ was produced by the ${}^{233}\mathrm{U}{(}^3\mathrm{He}{,5n)}^{231}\mathrm{Pu}$ reaction. After chemical separation, the ${}^{231}\mathrm{Pu}$ decay modes were studied using $\alpha$-spectrometry. The isotope, ${}^{231}\mathrm{Pu},$ was unequivocally identified by the $\alpha$-decay of the chain members from its $\alpha$- and electron-capture daughters using the $\alpha -\alpha$-correlation technique. The half-life of ${}^{231}\mathrm{Pu}$ was determined to be $(8.6\mathrm{}\pm 0.5)$ min. An $\alpha$-group with an energy of $(6.72\mathrm{}\pm 0.03)$ MeV was assigned to ${}^{231}\mathrm{Pu}.$

• Received 24 December 1998

DOI:https://doi.org/10.1103/PhysRevC.59.3086