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 MeV 10 C on Be and C targets. After inelastic scattering, structures associated with excited states in 10 C 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 8 Be, α decay to 6 Be g.s. , and proton decay to the 2.345-MeV state of 9 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 Be and 45 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 B can be approximately described by sequential α decay to the 5 Li intermediate state. The 8.06-and 9.61-MeV 10 B states that decay into the d + 6 Li 2.186 channel are confirmed. Evidence for cluster structure in 13 N is obtained from a number of excited states that decay into the p + 3α exit channel.

Investigations of three-, four-, and five-particle decay channels of levels in light nuclei created using aC9beam

“…Coulomb final-state interactions may deflect the trajectories and thus suppress the yield near cos(θ)=1. Alternatively the enhancement near cos(θ k )=-1 may not be related to a sequential angular correlation but rather might be a signature of some "diproton" character of the decay similar to that observed for the 6.57-MeV state in 10 C [23]. The total decay width in the sequential scenario can be estimated as [14,15] …”

“…29(b)]. As these states are expected to have 2α cluster structure [23], then it is not surprising that a neutronpickup by 9 C (which does not have any 2α cluster structure) does not populate these states strongly.…”

“…29(b) show the locations of two states (5.222 and 6.553 MeV) that were excited via the inelastic scattering of a 10 C beam and which decay by proton emission to the 9 B ground state [23]. These states dominated the total 10 C excitation energy spectrum in inelastic scattering, but here they are weakly populated and require a gate by the 9 B g.s.…”

“…29(a) and is dominated by a peak at 9.69 MeV, although other smaller peaks are evident. In our previous work, levels for this exit channel were revealed by gating on the presence of various narrow intermediate states [23]. Figures 29(b), 29(c), and 29(d) show the 10 C excitation-energy distribution gated on the 9 B ground state, the 6 Be ground state, and the 2.345-MeV 9 B excited state, respectively.…”

Continuum spectroscopy of light nuclei

“…For example in the 9 C+ 9 Be reaction at E/A=70 MeV studied with the HiRA detectors [17], we have identified 42 resonances in the continuum which decay into exit channels containing charged particle. These resonances are continuum states in 5,6,7 Li,6,7,8 Be,7,8,9 B, and 8,9,10 C nuclei. Of these, only half were associated with 201 , 0600 (2016) EPJ Web of Conferences…”