Relativistic QRPA description of isoscalar compression modes in open-shell nuclei in the A$\approx$60 mass region

Abstract

Very recent inelastic $\alpha$-scattering data on the isoscalar monopole and dipole strength distributions in ${}^{56}$Fe, ${}^{58}$Ni, and ${}^{60}$Ni are analyzed in the relativistic quasiparticle random-phase approximation (RQRPA) with the DD-ME2 effective nuclear interaction (nuclear matter compression modulus K${}_{nm}=251$ MeV). In all three nuclei the calculation nicely reproduces the observed asymmetric shapes of the monopole strength, and the bimodal structure of the dipole strength distributions. The calculated centroid and mean energies are in very good qualitative agreement with the experimental values both for the monopole, and for the low- and high-energy components of the dipole transition strengths. It is noted, however, that while DD-ME2 reproduces in detail the excitation energies of the giant monopole resonances (GMR) in nuclei with $A\ge 90$, the theoretical centroids are systematically above the experimental values in lighter nuclei with $A\le 60$. The latter can be reproduced with an effective interaction with a lower value of K${}_{nm}\approx$ 230 MeV but, because of the asymmetric shapes and pronounced fragmentation of the monopole strength distributions, isoscalar GMR data in light nuclei cannot provide accurate estimates of the nuclear matter compression modulus.

14 pages, 4 figures, submitted to Phys. Rev. C

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Cited by in corpus (7)

• Exotic modes of excitation in atomic nuclei far from stability
• Incompressibility in finite nuclei and nuclear matter
• Role of deformation on giant resonances within the QRPA approach and the Gogny force
• Low-energy isovector and isoscalar dipole response in neutron-rich nuclei
• Feasibility of the finite amplitude method in covariant density functional theory
• Continuum Random Phase Approximation for Relativistic Point Coupling Models
• Isoscalar dipole coherence at low energies and forbidden E1 strength