Magnetic dipole moments as a strong signature for α-clustering in even-even self-conjugate nuclei

We investigate the magnetic dipole moments in even-even self-conjugate nuclei from C-12 to Cr-48. For these nuclei, the measured gyromagnetic factors of excited states turn out to assume the same value of g approximate to +0.5 within statistical errors. This peculiar feature can be interpreted on the basis of collective excitations of alpha-clusters. Analogously, the behaviour of the same observable is studied for all isotopes obtained by adding one or two neutrons to the considered self-conjugate nuclei. It is found that for the N = Z + 1 isotopes the alpha-cluster structure hardly contributes to the observed negative g-factor value, corroborating molecular alpha-cluster models. The addition of a further neutron, however, restores the original alpha-cluster g-factors, except for the semi-magic isotopes, in which the deviations from g approximate to +0.5 can be associated with the relevant shell closures. Secondly, we analyze the same observable in the framework of a macroscopic alpha-cluster model on a finite lattice of side length L. We focus on the discretization effects induced in the magnetic dipole moments of the 2(1)(+) and the 3(1)(-) states of C-12 at different values of the lattice spacing a.

Automated summary

We investigate the magnetic dipole moments in even-even self-conjugate nuclei, finding that nuclei with the same characteristic have gyromagnetic factors close to +0.5, which can be explained by alpha-cluster collective excitations. For N = Z + 1 isotopes, the alpha-cluster structure has little contribution to the negative gyromagnetic factors, while adding another neutron restores the original factors. Additionally, discretization effects on magnetic dipole moments are analyzed using a macroscopic alpha-cluster model on a finite lattice.