Ground-state proton radioactivity has been identified from ${}^{121}\mathrm{Pr}$. A transition with a proton energy of $E_p=882(10)\mathrm{keV}$ [$Q_p=900(10)\mathrm{keV}$] and half-life $t_{1/2}={10}_{-3}^{+6}\mathrm{ms}$ has been observed and is assigned to the decay of a highly prolate deformed $3/2^{+}$ or $3/2^{-}$ Nilsson state. The present result is found to be incompatible with a previously reported observation of ground-state proton radioactivity from ${}^{121}\mathrm{Pr}$, which would have represented the discovery of this phenomenon.

• Received 12 April 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.032502