Emergence of low-energy monopole strength in the neutron-rich calcium isotopes
arXiv:1707.07185 · doi:10.1103/PhysRevC.96.044314
Abstract
The isoscalar monopole response of neutron-rich nuclei is sensitive to both the incompressibility coefficient of symmetric nuclear matter and the density dependence of the symmetry energy. The main goal of this paper is to explore the emergence, evolution, and origin of low energy monopole strength along the even-even calcium isotopes: from 40Ca to 60Ca. The distribution of isoscalar monopole strength is computed in a relativistic random phase approximation (RPA) using three effective interactions that have been calibrated to the properties of finite nuclei and neutron stars. A non-spectral approach is adopted that allows for an exact treatment of the continuum without any reliance on discretization. For the stable calcium isotopes, no evidence of low-energy monopole strength is observed, even as the 1f7/2 neutron orbital is being filled and the neutron-skin thickness progressively grows. Further, in contrast to experimental findings, a mild softening of the monopole response with increasing mass number is predicted. Beyond 48Ca, a significant amount of low-energy monopole strength emerges as soon as the weak-binding neutron orbitals (2p and 1f5/2) become populated. The emergence and evolution of low-energy strength is identified with transitions from these weakly-bound states into the continuum. Moreover, given that models with a soft symmetry energy tend to reach the neutron-drip line earlier than their stiffer counterparts, we identify an inverse correlation between the neutron-skin thickness and the inverse energy weighted sum.
14 pages, 8 figures, and 5 tables
References in corpus (19)
- Neutron-Rich Nuclei in Heaven and Earth
- Exotic modes of excitation in atomic nuclei far from stability
- Constraints on the symmetry energy and on neutron skins from the pygmy resonances in 68Ni and 132Sn
- Building relativistic mean field models for finite nuclei and neutron stars
- Isotopic dependence of the giant monopole resonance in the even-A ^{112-124}Sn isotopes and the asymmetry term in nuclear incompressibility
- Pygmy dipole resonance as a constraint on the neutron skin of heavy nuclei
- Investigation of Pygmy Dipole Resonances in the Tin Region
- Incompressibility of neutron-rich matter
- Pygmy Resonances and Neutron Skins
- Nuclear charge radii: Density functional theory meets Bayesian neural networks
- Isoscalar giant resonances in the Sn nuclei and implications for the asymmetry term in the nuclear-matter incompressibility
- The Giant Monopole Resonance in the Sn Isotopes: Why is Tin so "Fluffy"?
- Why is Tin so soft?
- Giant Monopole Resonance in even-A Cd isotopes, the asymmetry term in nuclear incompressibility, and the "softness" of Sn and Cd nuclei
- Microscopic linear response calculations based on the Skyrme functional plus the pairing contribution
- The role of superfluidity in nuclear incompressibilities
- The Giant Monopole Resonance in Pb isotopes
- Pigmy resonance in monopole response of neutron-rich Ni isotopes ?
- Nuclear breathing mode in neutron-rich Nickel isotopes: sensitivity to the symmetry energy and the role of the continuum