Experimental investigation of $\alpha$-condensation in light nuclei
Abstract
Method: To examine signatures of this alpha-condensation, a compound nucleus reaction using 160, 280, and 400 MeV 16O beams impinging on a carbon target was used to investigate the 12C(16O,7a) reaction. This permits a search for near-threshold states in the alpha-conjugate nuclei up to 24Mg. Results: Events up to an alpha-particle multiplicity of 7 were measured and the results were compared to both an Extended Hauser-Feshbach calculation and the Fermi break-up model. The measured multiplicity distribution exceeded that predicted from a sequential decay mechanism and had a better agreement with the multi-particle Fermi break-up model. Examination of how these 7 alpha final states could be reconstructed to form 8Be and 12C(0_2+) showed a quantitative difference in which decay modes were dominant compared to the Fermi break-up model. No new states were observed in 16O, 20Ne, and 24Mg due to the effect of the N-alpha penetrability suppressing the total alpha-particle dissociation decay mode. Conclusion: The reaction mechanism for a high energy compound nucleus reaction can only be described by a hybrid of sequential decay and multi-particle breakup. Highly alpha-clustered states were seen which did not originate from simple binary reaction processes. Direct investigations of near-threshold states in N-alpha systems are inherently impeded by the Coulomb barrier prohibiting the observation of states in the N-alpha decay channel. No evidence of a highly clustered 15.1 MeV state in 16O was observed from (28Si*,12C(0_2+))16O(0_6+) when reconstructing the Hoyle state from 3 alpha-particles. Therefore, no experimental signatures for alpha-condensation were observed.
Keywords
Cite
@article{arxiv.1907.05471,
title = {Experimental investigation of $\alpha$-condensation in light nuclei},
author = {Jack Bishop and Tzany Kokalova and Martin Freer and L Acosta and M Assie and S Bailey and G Cardella and N Curtis and E De Filippo and D Dell'Aquila and S De Luca and L Francalanza and B Gnoffo and G Lanzalone and I Lombardo and N. S. Martorana and S Norella and A Pagano and E. V. Pagano and M. Papa and S. Pirrone and G Politi and F Rizzo and P Russotto and L Quattrocchi and R Smith and I Stefan and A Trifiro and M Trimarchi and G Verde and M Vigilante and C Wheldon},
journal= {arXiv preprint arXiv:1907.05471},
year = {2019}
}