Fine structure in theαdecay of189Bi

Abstract

A detailed $\ensuremath{\alpha}$-decay study was performed for ${}^{189m,g}$Bi produced in the reaction of ${}^{95}$Mo on ${}^{96}$Mo at 418 MeV. Evaporation residues were selected in-flight using the Argonne fragment mass analyzer and implanted into a double sided silicon strip detector. The correlation technique between implants and subsequent decays was used to observe new weak $\ensuremath{\alpha}$ branches of ${}^{189}$Bi to excited states in ${}^{185}$Tl. A more precise value of 182(8) keV for the excitation energy of the $\ensuremath{\pi}s$${}_{1/2}$ intruder state in ${}^{189}$Bi was determined. The $\ensuremath{\alpha}$ decay of the ${}^{189}$Bi (9/2${}^{\ensuremath{-}})$ ground state to the $\ensuremath{\pi}{d}_{3/2}$ level at 284 keV was observed for the first time. In addition, the $\ensuremath{\alpha}$ decay of ${}^{188}$Bi was remeasured. Reduced widths for the $\ensuremath{\alpha}$ decays of odd-$A$ ${}^{189\ensuremath{-}197m,g}$Bi nuclei to states in their Tl daughters are discussed.