Clustering effects in fusion evaporation reactions with light even-even N=Z nuclei

L Morelli ,G Pasquali ,M Bini ,M Degerlier ,A Olmi ,S Valdré ,M Bruno ,T Marchi ,Giuseppe Pastore ,D Fabris ,N Gelli ,F Gulminelli ,C Frosin ,S Piantelli ,S Barlini ,G Casini ,M Dʼagostino ,M Cinausero ,F Gramegna ,E Vardaci

doi:10.1088/1742-6596/863/1/012022

Abstract

In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. In the currently experimental campaign, the NUCL-EX collaboration has measured the12C+12C and14N+10B reactions at 95 MeV and 80 MeV respectively. The experimental data corresponding to complete fusion of target and projectile into an excited24Mg nucleus was compared to the results of a pure statistical model [3, 4]. In addition, data from12C+12C have been analyzed to investigate the decay of the Hoyle state of12C* [12] obtained as an intermediate step in the 6α decay channel of the24Mg* formed in central events.

Highlights

The NUCL-EX collaboration has recently started an experimental campaign of exclusive measurements of fusion-evaporation reactions with light nuclei as interacting partners
Energy spectra for protons and α particles detected at GARFIELD angles are plotted in figure 1, for residues of different charge, for the 14N reaction, and compared to HF [4] calculations and to data for the 12C+12C reaction
Some discrepancies are present in events with an Oxygen residue, where the energy tails for α particles are not reproduced by the model, especially for the 12C+12C case

Summary

INTRODUCTION

The NUCL-EX collaboration has recently started an experimental campaign of exclusive measurements of fusion-evaporation reactions with light nuclei as interacting partners. Despite the interest of this issue, few studies, mainly based on inclusive experiments, exist on the evaporation of very light nuclei (A ∼ 20 region) at relatively high excitation energy (ε∗ ≈ 3 A.MeV). Some excited states of different nuclei in this mass region are known to present pronounced cluster structures These correlations may persist in the ground state along some selected isotopic chains [6] and, according to the Ikeda diagrams [2], α-clustered excited states are sizeably expected at high excitation energies close to the multi-alpha decay threshold in all even-even N = Z nuclei. Concerning experimental research, rotational bands consistent with α-cluster structures have been identified in different even-even light nuclei and shown to persist even along their isotopic chains Such effects can be experimentally seen as an excess of cluster production with respect to the prediction of the statistical model, provided that the ingredients of the latter are sufficiently constrained via experimental data. It is interesting for such systems that they can be studied at different beam energies, extracting information on how (and to what extent) structure effects are still at play in the decay of hot nuclei at different excitation regimes

THE EXPERIMENTS

RESULTS

The Hoyle state in peripheral collisions

Conclusions and perspectives