Two-proton decay from α -cluster states in C10 and N11

Abstract

Two-proton decay from excited states in $^{10}\mathrm{C}$ and $^{11}\mathrm{N}$ has been characterized from an analysis of the $2p+2\ensuremath{\alpha}$ and $3p+2\ensuremath{\alpha}$ exit channels. Data from four previously published invariant-mass studies associated with inelastic excitation, multinucleon knockout, and neutron pickup reactions have been considered. A rotational band in $^{10}\mathrm{C}$ was identified built on the second ${0}^{+}$ state which has strong $\ensuremath{\alpha}$-cluster molecular structure. The members of this band were tentatively identified up to ${J}^{\ensuremath{\pi}}={4}^{+}$ and all identified states have a prompt $2p$ decay branch. The spins of the ${0}^{+}$ and ${2}^{+}$ members were deduced from comparisons of the momentum correlations in their $2p$ branches to those from known $2p$ emitters. The ${2}^{+}$ and the tentative ${4}^{+}$ members are both above the $\ensuremath{\alpha}$ threshold and exhibit large reduced decay widths for $\ensuremath{\alpha}$ emission. This band exhibits a similar moment of inertia to its analog in the mirror nucleus $^{10}\mathrm{Be}$. Evidence is also presented for a molecular band in $^{11}\mathrm{N}$ built on the second $3/{2}^{\ensuremath{-}}$ state which $2p$ decays. Tentative members of this band have been assigned up to ${J}^{\ensuremath{\pi}}=9/{2}^{\ensuremath{-}}$ and their excitation energies also match their likely analogs in the mirror nucleus $^{11}\mathrm{Be}$.