αdecay of theπh11/2isomer inIr164

Abstract

The $\ensuremath{\alpha}$-decay branch of the $\ensuremath{\pi}{h}_{11/2}$ isomer in $^{164}\mathrm{Ir}$ has been identified using the GREAT spectrometer. The $^{164}\mathrm{Ir}$ nuclei were produced using the ${}^{92}\text{Mo}({}^{78}\text{Kr},p5n){}^{164}\text{Ir}$ reaction and separated in flight using the recoil ion transport unit (RITU) gas-filled separator. The measured $\ensuremath{\alpha}$-decay energy of $6880\ifmmode\pm\else\textpm\fi{}10$ keV allowed the excitation of the $\ensuremath{\pi}{h}_{11/2}$ state in $^{160}\mathrm{Re}$ to be deduced as $166\ifmmode\pm\else\textpm\fi{}14$ keV. The half-life of $^{164}\mathrm{Ir}$ was measured with improved precision to be $70\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}$s and an $\ensuremath{\alpha}$-decay branching ratio of $4\ifmmode\pm\else\textpm\fi{}2$% was determined. Improved half-life and branching ratio measurements were also obtained for $^{165}\mathrm{Ir}$, but no evidence was found for the ground-state decays of either $^{164}\mathrm{Ir}$ or $^{165}\mathrm{Ir}$.