Isoscalar giant resonances in the Sn nuclei and implications for the asymmetry term in the nuclear-matter incompressibility

TL;DR

This study measured isoscalar giant resonances in Sn isotopes using alpha scattering to better understand nuclear incompressibility and the asymmetry term, revealing discrepancies with theoretical models and estimating K_{tau}.

Contribution

It provides new experimental data on giant resonances in Sn isotopes and constrains the asymmetry term in nuclear incompressibility, informing nuclear structure models.

Findings

Centroid energies of ISGMR are lower than theoretical predictions.

Estimated K_{tau} = -550 ± 100 MeV for the asymmetry term.

Experimental spectra obtained over a wide angular and energy range.

Abstract

We have investigated the isoscalar giant resonances in the Sn isotopes using inelastic scattering of 386-MeV alpha-particles at extremely forward angles, including 0deg. We have obtained completely "background-free inelastic-scattering spectra for the Sn isotopes over the angular range 0deg--9deg and up to an excitation energy of 31.5 MeV. The strength distributions for various multipoles were extracted by a multipole decomposition analysis based on the expected angular distributions of the respective multipoles. We find that the centroid energies of the isoscalar giant monopole resonance (ISGMR) in the Sn isotopes are significantly lower than the theoretical predictions. In addition, based on the ISGMR results, a value of K_{tau} = -550 \pm 100 MeV is obtained for the asymmetry term in the nuclear incompressibility. Constraints on interactions employed in nuclear structure calculations are discussed on the basis of the experimentally-obtained values for K_(infty) and K_(tau).