First Observation of the β3αp Decay of O13

The $\ensuremath{\beta}$-delayed proton decay of $^{13}\mathrm{O}$ has previously been studied, but the direct observation of $\ensuremath{\beta}$-delayed $3\ensuremath{\alpha}p$ decay has not been reported. Rare $3\ensuremath{\alpha}p$ events from the decay of excited states in $^{13}{\mathrm{N}}^{\ensuremath{\star}}$ provide a sensitive probe of cluster configurations in $^{13}\mathrm{N}$. To measure the low-energy products following $\ensuremath{\beta}$-delayed $3\ensuremath{\alpha}p$ decay, the Texas Active Target (TexAT) time projection chamber was employed using the one-at-a-time $\ensuremath{\beta}$-delayed charged-particle spectroscopy technique at the Cyclotron Institute, Texas A University. A total of $1.9\ifmmode\times\else\texttimes\fi{}{10}^{5}$ $^{13}\mathrm{O}$ implantations were made inside the TexAT time projection chamber. A total of 149 $3\ensuremath{\alpha}p$ events were observed, yielding a $\ensuremath{\beta}$-delayed $3\ensuremath{\alpha}p$ branching ratio of 0.078(6)%. Four previously unknown $\ensuremath{\alpha}$-decaying excited states were observed in $^{13}\mathrm{N}$ at 11.3, 12.4, 13.1, and 13.7 MeV decaying via the $3\ensuremath{\alpha}+p$ channel.