Continuum spectroscopy with aC10beam: Cluster structure and three-body decay

Abstract

Resonance-decay spectroscopy is used to study particle-unbound excited states produced in interactions of $E/A=10.7 \mathrm{MeV}$ $^{10}\mathrm{C}$ on Be and C targets. After inelastic scattering, structures associated with excited states in $^{10}\mathrm{C}$ were observed at 5.22, 5.29, 6.55, 6.56, 6.57, and 8.4 MeV which decay into the $2p+2\ensuremath{\alpha}$ final state. This final state is created via a number of different decay paths, which include prompt and sequential two-proton decay to the ground state of $^{8}\mathrm{Be}$, $\ensuremath{\alpha}$ decay to $^{6}\mathrm{Be}{}_{\mathrm{g}.\mathrm{s}.}$, and proton decay to the 2.345-MeV state of $^{9}\mathrm{B}$. For the sequential two-proton decay states (5.22 and 6.55 MeV), angular correlations between the first two decay axes indicate that the spin of these states are nonzero. For the prompt two-proton decay of the 5.29-MeV state, the three-body correlations between the two protons and the core are intermediate between those measured for ground-state $^{6}\mathrm{Be}$ and $^{45}\mathrm{Fe}$ decays. The 6.55- and 6.57-MeV structures are most probably associated with the same level, which has a 14% two-proton decay branch with a strong ``diproton'' character and a 86% sequential two-proton decay branch. Correlations between the fragments following the three-body decay of the 2.345-MeV state of $^{9}\mathrm{B}$ can be approximately described by sequential $\ensuremath{\alpha}$ decay to the $^{5}\mathrm{Li}$ intermediate state. The 8.06- and 9.61-MeV $^{10}\mathrm{B}$ states that decay into the $d+^{6}\mathrm{Li}{}_{2.186}$ channel are confirmed. Evidence for cluster structure in $^{13}\mathrm{N}$ is obtained from a number of excited states that decay into the $p+3\ensuremath{\alpha}$ exit channel.