Investigation of the isoscalar response of $^{24}\mathrm{Mg}$ to $^{6}\mathrm{Li}$ scattering
Résumé
Background: is a strongly deformed nucleus in the ground state. Deformation effects can be observed in the structure of the isoscalar giant monopole and quadrupole resonances. is also a nucleus that is well known to present different types of cluster-oscillation modes. Both giant resonances and cluster states are strongly populated by isoscalar transitions.
Purpose: To extract the , , and transition strengths via scattering. The probe is a powerful tool for investigating the isoscalar nuclear response with a very favorable ratio of resonance-to-continuum background.
Method: Double-differential cross sections of inelastic scattering, at the beam energy of 100 MeV/u, were measured in the excitation-energy range and scattering angles . A multipole-decomposition analysis was performed for extracting the isoscalar , , and strength distributions.
Results: The extracted multipole strengths were compared with predictions from consistent quasiparticle random phase approximation calculations. The theoretical predictions are in fair agreement with the experimental data. The strength was also compared with results from antisymmetrized molecular dynamics calculations found in the literature. A few peaks in the experimental data might be associated with clustering in .
Conclusions: Ground-state deformation effects were observed in the isoscalar giant monopole resonance (ISGMR) and isoscalar giant quadrupole resonance (ISGQR) distributions. The ISGMR strength is split in two peaks around 19 and 28 MeV. The ISGQR exhibits a pronounced peak at 20 MeV with a broadening at the low-energy region, similar to predictions from microscopic calculations. Signatures of excitation of cluster states were observed in the response. Further studies including particle-decay measurements will be required to confirm the nature of the observed peaks.