Isomer decay tagging in the heavy nuclei:Ra210andRa209

Abstract

Excited states in $^{210}\mathrm{Ra}$ and $^{209}\mathrm{Ra}$ were populated using the $^{184}\mathrm{W}(^{30}\mathrm{Si},xn)$ reaction at $148\phantom{\rule{0.3em}{0ex}}\text{MeV}$ beam energy. Fusion evaporation recoils were selected using the gas-filled spectrometer, SASSYER. Prompt $\ensuremath{\gamma}$ rays were detected using Compton-suppressed Ge detectors from the YRAST Ball array surrounding the target. Delayed $\ensuremath{\gamma}$ rays, following isomeric decays, were detected at the focal plane of SASSYER with a smaller array of Ge detectors. The decay energy and lifetime for the ${8}^{+}{(\ensuremath{\pi}{h}_{9∕2})}^{n}$ isomer of $^{210}\mathrm{Ra}$ were determined; values for the yrast $B(E2;{8}^{+}\ensuremath{\rightarrow}{6}^{+})$ in $^{210}\mathrm{Ra}$ and neighboring nuclei are interpreted within the seniority scheme. This isomer was also used to select $\ensuremath{\gamma}$-rays deexciting levels above the isomeric state in $^{210}\mathrm{Ra}$. In addition, transitions in $^{209}\mathrm{Ra}$ were identified for the first time. Two high-spin isomers are suggested to exist in this isotope.