Skin Thickness Of Nuclei Research Articles

The neutron skin thickness in nuclei with clustering at low densities

This study concentrates on searching for a dependable, fully microscopic theory to find out new behaviours and understand their consequences for theoretical pictures. The models for nuclear structure are tested, refined and developed by acquiring new data [1][2][3]. This data is useful for astrophysical calculations and predictions. In density functional theories, including the ETF theory, the equation of state (EOS) of symmetric nuclear matter (SNM), is an important measure. Empirically, we receive information about quantities relating to SNM, all these measures are thoroughly tested. In the absence of any unswerving knowledge below this density we shall take that energy still rises up to some density, neglecting possible small fluctuations, as the density is brought down. Our discussion at the moment is without the Coulomb forces applicable only for the hypothetical nuclear matter; they are added finally to correctly portray the actual picture in nuclei. Our approach in this study is macroscopic. This work concludes that the neutron skin thickness in nuclei is found to reduce significantly, for the reason of clustering.

NEUTRON SKIN THICKNESS IN NEUTRON-RICH NUCLEI: BULK AND SURFACE CONTRIBUTIONS AND SHELL EFFECTS

We analyze theoretically the neutron skin thickness in nuclei and its correlation with the symmetry energy by using semiclassical and mean field approaches together with nuclear effective interactions. Semiclassical approaches reveal that the neutron skin thickness in nuclei is formed by a combination of bulk and surface contributions. To investigate the neutron skin thickness predicted by mean field models, we fit the corresponding densities by two-parameter Fermi distributions. Using these parametrized densities, we study the neutron skin thickness as well as its bulk and surface contributions in 208 Pb and in Zr isotopes, where the influence of shell effects along the isotopic chain is discussed.

Nuclear matter properties, phenomenological theory of clustering at the nuclear surface, and symmetry energy

We present a phenomenological theory of nuclei that incorporates clustering at the nuclear surface in a general form. The theory explains the recently extracted large symmetry energy by Natowitz et al., at low densities of nuclear matter and is fully consistent with the static properties of nuclei. In a phenomenological way, clusters of all sizes and shapes along with medium modifications are included. Symmetric nuclear matter properties are discussed in detail. Arguments are given that lead to an equation of state of nuclear matter consistent with clustering in the low-density region. We also discuss properties of asymmetric nuclear matter. Because of clustering, an interesting interpretation of the equation of state of asymmetric nuclear matter emerges. As a framework, an extended version of Thomas-Fermi theory is adopted for nuclei which also contain phenomenological pairing and Wigner contributions. This theory connects the nuclear matter equation of state, which incorporates clustering at low densities, with clustering in nuclei at the nuclear surface. Calculations are performed for various equations of state of nuclear matter. We consider measured binding energies of 2149 nuclei for $N$, $Z$ \ensuremath{\geqslant} 8. The importance of the quartic term in symmetry energy is demonstrated at and below the saturation density of nuclear matter. It is shown that it is largely related to the use of, ab initio, a realistic equation of state of neutron matter, particularly the contribution arising from the three neutron interactions and somewhat to clustering. Reasons for these are discussed. Because of clustering the neutron skin thickness in nuclei is found to reduce significantly. The developed theory predicts situations and regimes to be explored both theoretically and experimentally.

Clustering at the nuclear surface and symmetry energy

With in the energy density functional formalism a phenomenological theory of nuclei is developed which incorporates clustering at the nuclear surface in a general form. This explains the large values of symmetry energy extracted recently at low values of nuclear matter density. It is shown that the nuclear matter binding energy per nucleon (B/A), in the neighbourhood of zero density, must approach its value at the saturation density. The parameters of the theory are mainly constrained from the binding energies and root mean square radii of 376 spherical nuclei as well as the large values of the recently extracted symmetry energy at low densities. Importance of quartic term in symmetry energy is demonstrated. It is shown that it originates due to clustering as well as due to contribution of three-nucleon interaction in the state-of-the-art equation of state of neutron matter at and below the saturation densities. It is found that clustering significantly reduces the neutron skin thickness in nuclei.

Interaction of low-energy neutrons with Nd isotopes

Low-energy neutron data for even-even isotopes 1142–150Nd are considered. It is shown that the diffuseness parameter noticeably changes in going from one isotope to another (from a = 0.55 fm for 142Nd to a = 0.75 fm for 150Nd), which agrees with the theoretical indications of a decrease in the skin thickness for nuclei with closed shells. The analysis points to the possible existence of the semimagic number Z = 58.