Charge radii of potassium isotopes in the RMF(BCS)* approach

We apply the recently proposed RMF(BCS)* ansatz to study the charge radii of the potassium isotopic chain up to $^{52}$K. It is shown that the experimental data can be reproduced rather well, qualitatively similar to the Fayans nuclear density functional theory, but with a slightly better description of the odd-even staggerings (OES). Nonetheless, both methods fail for $^{50}$K and to a lesser extent for $^{48,52}$K. It is shown that if these nuclei are deformed with a $\beta_{20}\approx-0.2$, then one can obtain results consistent with experiments for both charge radii and spin-parities. We argue that beyond mean field studies are needed to properly describe the charge radii of these three nuclei, particularly for $^{50}$K.

Cluster decay half-lives using asymmetry dependent densities

Adopting different neutron and proton density distributions the cluster decay half-lives have been investigated using double-folding potentials with constant and nuclear asymmetry dependent sets of the parameters of nuclear densities. Two adopted asymmetry dependent sets of the parameters are fitted based on the microscopic calculations and calculated based on the neutron skin/halo-type nuclei assumption and employing experimental rms charge radii. The bulk agreement between theory and experiment has been obtained for entire sets of parameters using calculated cluster preformation probability. The very little differences between skin and halo-type assumption have been observed. However, the notable role of the asymmetry parameter has been seen in relatively large differences between the skin and skin-type with zero thickness.

Nuclear Structure Evolution Reflected from Local Relations

The structure evolution of nuclei which are in connection with symmetry breaking is one of the important problems not only for nuclear structures, but also for astrophysics and the spectroscopy of exotic nuclei. Many physical quantities can provide useful information of a shell structure, such as nuclear masses and nuclear charge radii. This paper introduces three kinds of local relations, i.e., the NpNn scheme respectively for the quadrupole deformation parameter and the excitation energy of the first 2+, 4+, 6+ states, the (αN′n+N′p) relation for nuclear charge radii and α decay energies, and the so-called “nonpairing” relation for binding energies and nuclear charge radii. All these relations reflect the evolution of nuclear structures, involving shells, subshells, shape coexistence, phase transition and the Wigner effect. Some results from different models can be verified with each other.

Laser spectroscopy of light muonic atoms and the nuclear charge radii

The energy levels of hydrogen-like atomic systems are shifted slightly by the complex structure of the nucleus, in particular by the finite size of the nucleus. These energy shifts are vastly magnified in muonic atoms and ions, i.e. the hydrogen-like systems formed by a negative muon and a nucleus. By measuring the 2S-2P energy splitting in muonic hydrogen, muonic deuterium and muonic helium, we have been able to deduce the p, d, ^33He and ^44He nuclear charge radii to an unprecedented accuracy. These radii provide benchmarks for hadron and nuclear theories, lead to precision tests of bound-state QED in regular atoms and to a better determination of the Rydberg constant.

Evidence of a sudden increase in the nuclear size of proton-rich silver-96

Understanding the evolution of the nuclear charge radius is one of the long-standing challenges for nuclear theory. Recently, density functional theory calculations utilizing Fayans functionals have successfully reproduced the charge radii of a variety of exotic isotopes. However, difficulties in the isotope production have hindered testing these models in the immediate region of the nuclear chart below the heaviest self-conjugate doubly-magic nucleus 100Sn, where the near-equal number of protons (Z) and neutrons (N) lead to enhanced neutron-proton pairing. Here, we present an optical excursion into this region by crossing the N = 50 magic neutron number in the silver isotopic chain with the measurement of the charge radius of 96Ag (N = 49). The results provide a challenge for nuclear theory: calculations are unable to reproduce the pronounced discontinuity in the charge radii as one moves below N = 50. The technical advancements in this work open the N = Z region below 100Sn for further optical studies, which will lead to more comprehensive input for nuclear theory development.