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.

References in corpus (18)

• Alpha cluster condensation in 12C and 16O
• Properties of ${}^{12}$C in the {\it ab initio} nuclear shell-model
• Microscopic Clustering in Light Nuclei
• Structure and rotations of the Hoyle state
• Four-particle condensate in strongly coupled fermion systems
• Structure of ground and excited states of ${}^{12}$C
• Evidence for Triangular D_3h Symmetry in 12C
• Unambiguous Identification of the Second 2+ State in 12C and the Structure of the Hoyle State
• Dilute Multi Alpha Cluster States in Nuclei
• Concepts of alpha-particle condensation
• Extended Hauser-Feshbach Method for Statistical Binary-Decay of Light-Mass Systems
• Status of Alpha-Particle Condensate Structure of the Hoyle State
• Evidence for $\alpha$-particle condensation in nuclei from the Hoyle state deexcitation
• High precision probe of the fully sequential decay width of the Hoyle state in ${}^{12}$C
• Mass and charge identification of fragments detected with the Chimera Silicon-CsI(Tl) telescopes
• Critical Temperature for $\alpha$-Particle Condensation within a Momentum Projected Mean Field Approach
• Critical temperature for $\alpha$-particle condensation in asymmetric nuclear matter
• Alpha-Particle condensation in nuclear systems: present status and perspectives

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