12C and α-clusters, 0+ spectrum, and Hoyle-state candidates in 24Mg
Abstract
Background: A recent inelastic alpha-scattering experiment [Phys. Rev. Lett. 129, 102701 (2022)] found 0+ resonances in 24Mg on and above the 12C+12C break-up threshold. It has been conjectured that the states have a 12C+12C cluster structure, and play a similar role in accelerating 12C+12C fusion to the manner in which the Hoyle state accelerates production of 12C in massive stars. Purpose: We wish to build up a quantitative theoretical basis for the considerations of the Hoyle-state paradigm, by calculating the distribution of the 0+ states in the shell, as well as in the relevant cluster models. Methods: We determine the spectrum of excited 0+ states in 24Mg nucleus using multiconfigurational dynamical symmetry calculations leading to a unified description of the quartet (or shell), 12C+12C and 20Ne+4He cluster configurations. Results: The density of 0+ states in the quartet spectrum is comparable to that found in experiment; however, the density of cluster states is considerably less. Conclusions: The recently observed alpha-scattering resonances do not seem to be simple 12C+12C cluster states, but are more plausibly interpreted as fragmented cluster states due to coupling to quartet excitations, as background states.
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