6533b86efe1ef96bd12cc6e3

RESEARCH PRODUCT

αdecay studies of very neutron-deficient francium and radium isotopes

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description

Very neutron-deficient francium and radium isotopes have been produced in fusion evaporation reactions using $^{63}\mathrm{Cu}$ and $^{65}\mathrm{Cu}$ ions on $^{141}\mathrm{Pr}$ targets and $^{36}\mathrm{Ar}$ ions on $^{170}\mathrm{Yb}$ targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam. The activities were implanted into a position-sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and decays. Two new \ensuremath{\alpha} decaying radium isotopes, $^{201}\mathrm{Ra}$ and $^{202}\mathrm{Ra}$, were identified. The \ensuremath{\alpha} decay energy and half-life of $^{203}\mathrm{Ra}$ were measured with improved precision. The \ensuremath{\alpha} decay properties measured for the francium isotopes $^{201}\mathrm{Fr},^{202}\mathrm{Fr},^{203}\mathrm{Fr}$, and $^{204}\mathrm{Fr}$ were confirmed, in many cases with improved precision. For the first time, a $(\ensuremath{\pi}{s}_{1/2}^{\ensuremath{-}1})1/{2}^{+}$ proton intruder state was identified in francium isotopes, namely in $^{201}\mathrm{Fr}$ and tentatively in $^{203}\mathrm{Fr}$. The measured decay properties for the neutron-deficient odd-mass Fr isotopes suggest an onset of substantial deformation at $N=112$.