Resonances in ${}^{12}$C and ${}^{24}$Mg: what do we learn from a microscopic cluster theory?

Abstract

We discuss resonance properties in three-body systems, with examples on ${}^{12}\mathrm{C}$ and ${}^{24}\mathrm{Mg}$. We use a microscopic cluster model, where the generator coordinate is defined in the hyperspherical formalism. The ${}^{12}\mathrm{C}$ nucleus is described by an $\alpha +\alpha +\alpha$ structure, whereas ${}^{24}\mathrm{Mg}$ is considered as an ${}^{16}\mathrm{O}+\alpha +\alpha$ system. We essentially pay attention to resonances. We review various techniques which may extend variational methods to resonances. We consider $0^{+}$ and $2^{+}$ states in ${}^{12}\mathrm{C}$ and ${}^{24}\mathrm{Mg}$. We show that the r.m.s. radius of a resonance is strongly sensitive to the variational basis. This has consequences for the Hoyle state ($0_2^{+}$ state in ${}^{12}\mathrm{C}$) whose radius has been calculated or measured in several works. In ${}^{24}\mathrm{Mg}$, we identify two $0^{+}$ resonances slightly below the three-body threshold.

8 pages, 6 figures, accepted for publication at EPJA

References in corpus (5)

• Recent developments in no-core shell-model calculations
• A high-precision variational approach to three- and four-nucleon bound and zero-energy scattering states
• Local versus nonlocal $\alpha \alpha$ interactions in $3\alpha$ description of ${}^{12}$C
• Gas-like state of $\alpha$ clusters around ${}^{16}$O core in ${}^{24}$Mg
• Microscopic three-cluster study of light exotic nuclei

Cited by in corpus (2)

• Semi-microscopic construction of multi-$\alpha$ cluster spaces
• Fusion and reactions of $\alpha$+${}^8$Be in the Hoyle resonance and associated resonances region