Continuum spectroscopy with a C10 beam: Cluster structure and three-body decay

Resonance-decay spectroscopy is used to study particle-unbound excited states produced in interactions of E/A=10.7-MeV C10 on Be and C targets. After inelastic scattering, structures associated with excited states in C10 were observed at 5.22, 5.29, 6.55, 6.56, 6.57, and 8.4 MeV which decay into the 2p+2α 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 Be8, α decay to Be6g.s., and proton decay to the 2.345-MeV state of B9. 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 Be6 and Fe45 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 B9 can be approximately described by sequential α decay to the Li5 intermediate state. The 8.06- and 9.61-MeV B10 states that decay into the d+Li62.186 channel are confirmed. Evidence for cluster structure in N13 is obtained from a number of excited states that decay into the p+3α exit channel.