Investigation of decay modes of argon isotopes formed in fusion-evaporation reactions.

Mabiala J., Cicerchia M., Marchi T., Gramegna F., Cinausero M., Bermudez J., Fabris D., Pino F., Degerlier M., Bruno M., D'Agostino M., Morelli L., Barlini S., Bini M., Casini G., Gelli N., Olmi A., Pasquali G., Pastore G., Camaiani A., Piantelli S., Valdré S., Gruyer D., Cieplicka N., Vardaci E., Davide F., Quero D., Decanditis B., Ashad M., Swartz J.A., Mantovani G.
  Mercoledì 28/09   10:00 - 13:00   Edificio Psicologia 2 - Aula 3F   I - Fisica nucleare e subnucleare
The NUCL-EX collaboration has recently initiated an experimental campaign of exclusive measurements of fusion-evaporation reactions with light nuclei as interacting partners, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold. In light $\alpha$-like nuclei, clustering is observed as a general phenomenon at high excitation energy close to the $\alpha$-decay thresholds. In fact, this exotic behavior has been perfectly illustrated by the Ikeda diagram for even-even $N=Z$ nuclei, and has been later extended by von Oertzen for neutron-rich nuclei. Recently the ${}^{12}C$ (95 MeV) + ${}^{12}C$ and ${}^{14}N$ (80.7 MeV) + ${}^{10}B$$ reactions have been extensively investigated in order to study the decay pattern of the ${}^{24}Mg$ compound nucleus, populated at the same excitation energy but through different entrance channels. Out-of-equilibrium $\alpha$-emission has been evidenced even for more dissipative events in both reactions. This has been attributed to a possible presence of residual $\alpha$ correlations in the excited ${}^{24}Mg$ nucleus or to its daughter ${}^{20}Ne$, at excitation energies well above the energy threshold for full disintegration into $\alpha$-particles. To further investigate possible $\alpha$-clustering effects in reaction partners as well as cluster correlations in fused systems at high excitation energy, new measurements of ${}^{24}Mg$ (161 MeV) + ${}^{12}C$ and ${}^{24}Mg$ (142 MeV) + ${}^{13}C$ have been performed using the GARFIELD+RCo setup. The comparison between the two systems should give new insights on the influence of the neutron content on the decay mechanism. Preliminary experimental results and their comparison with model predictions will be discussed.