Levels inPo84204from the decay ofAt85204

Abstract

The electron-capture decay of $_{85}^{204}\mathrm{At}$ (9 min) has been studied by means of $\ensuremath{\gamma}$ and ${e}^{\ensuremath{-}}$ multiscaled singles and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence measurements with Ge(Li) and Si(Li) detector systems. The samples were produced by $\mathrm{Ir}(^{16}\mathrm{O}, xn)$ reactions and on-line isotope separation. About 50 $\ensuremath{\gamma}$-ray transitions have been assigned to the $^{204}\mathrm{At}$ decay, \ensuremath{\sim}35 of which have been placed in a proposed level scheme for $_{84}^{204}\mathrm{Po}$. The energy of the ${8}^{+}$\ensuremath{\rightarrow}${6}^{+}$ isomeric transition has been deduced to be 12.1 keV, and the half-life of the ${8}^{+}$ isomer has been measured to be 150\ifmmode\pm\else\textpm\fi{}10 ns. From these data, the $B(E2)$ value of this isomeric transition is found to be 3.7 Weisskopf units. The $^{204}\mathrm{At}$ ground state is assigned an ${I}^{\ensuremath{\pi}}$ value of ${7}^{+}$, which eliminates the need for some low-energy levels in $^{204}\mathrm{At}$ and $^{200}\mathrm{Bi}$ that were tentatively proposed in recent data evaluations, where a ${5}^{+}$ assignment was made.RADIOACTIVITY $^{204}\mathrm{At}$ from $\mathrm{Ir}(^{16}\mathrm{O}, xn)$; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ICC, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}\ensuremath{-}t$, isomeric lifetime in $^{204}\mathrm{Po}$; $^{204}\mathrm{Po}$ deduced levels, $J$, $\ensuremath{\pi}$; $^{204}\mathrm{At}$ ground state deduced $J$, $\ensuremath{\pi}$; Ge(Li) and Si(Li) detectors; on-line isotope-separated sources.