Measurements of ISGMR in Sn, Cd and Pb isotopes and the asymmetry of nuclear matter incompressibility

Abstract

The compression-mode isoscalar giant monopole resonance (ISGMR) has been studied in the Sn, Cd and Pb isotopes using inelastic scattering of 400 MeV α-particles at extreme forward angles, including .We have obtained completely ``background-free'' inelastic-scattering spectra for the Sn, Cd, and Pb isotopes for a wide angular and excitation-energy range. The various giant resonances excited with different transferred angular momenta were extracted by a multipole-decomposition analysis (MDA). It was found that the centroid energies of the ISGMR in Sn isotopes are significantly lower than the theoretical predictions. The K τ in the empirical expression for the nuclear incompressibility has been determined to be MeV from the moment ratios [1]. The extracted value for the Cd isotopes isMeV. These numbers are consistent with values of MeV obtained from an analysis of the isotopic transport ratios in medium-energy heavy-ion reactions [2], MeV obtained from constraints placed by neutron-skin data from anti-protonic atoms across the mass table [3], and MeV obtained from theoretical calculations using different Skyrme interactions and relativistic mean field (RMF) Lagrangians [4].Stringent constraints on interactions employed in nuclear structure calculations are obtained on the basis of the experimentally determined values for and . These parameters constrain as well the equation of state (EOS) of nuclear matter. However, a significant discrepancy still remains. The ISGMR positions in Sn and Cd isotopes are systematically lower than the predictions obtained on basis of determined from the ISGMR in 208 Pb. This raises the question "why are Sn and Cd nuclei so soft?", an important problem that has to be solved [5]. For a clue to solve the problem, the exact positions of the ISGMR in 204, 206, 208 Pb have to be measured [6].In this talk, we will review the current status of the experimental studies on the compressionmode giant resonances, and the possible implications for astrophysics and physics with exotic nuclei.[1] T. Li et al., Phys.

Isoscalar Giant Monopole Resonance in Spherical Nuclei as a Nuclear Matter Incompressibility Indicator

“…The values of the centroid energies for Sn isotopes obtained from calculations with three Skyrme interactions (SLy4, SGII, Sk3) are listed in Table 2. It can be seen from Table 1 that a very good agreement with the experimental data for 56,58,60 Ni is obtained, while the results with both Skyrme interactions underestimate the experimental energy of the soft monopole vibrations of 68 Ni. The excitation energy of this ISGMR in 68 Ni is located unexpectedly at higher energy (21.1 MeV) for the Ni isotopic chain, having at the same time large error bars.…”

“…We present and discuss the values of the centroid energies in Sn isotopic chain (A=112-124) studying its isotopic sensitivity. The main reason to select these chains of spherical nuclei is partly supported by their recent intensive ISGMR measurements so that we focus too on the comparison with the available experimental data for Ni [58], Sn [59], and Pb [60,61] isotopes.…”