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

Abstract

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.

Universal trend of charge radii of even-even Ca–Zn nuclei

“…High-precision measurements of nuclear charge radii offer unique information on the structure of atomic nuclei and fundamental symmetries of nature [1,2]. In particular, the precise data on variations of charge radii with proton and neutron numbers shed light on elusive aspects of nuclear behavior, such as superfluidity [3][4][5][6], shell structure [7,8], and correlations [9,10].…”

Trends of neutron skins and radii of mirror nuclei from first principles

“…Recent high-precision measurements of charge radii in isotope chains of potassium [17], calcium [18,19], nickel [20], copper [21,22], and silver [23], have revealed that they carry information about changes in shell-structure, deformation, and pairing effects. Charge radii can be easily probed with the well-known electromagnetic interaction [24,25].…”

Impact of Nuclear Deformation and Pairing on the Charge Radii of Palladium Isotopes

“…Overall, all functionals describe the correct general smooth parabolic behavior of the measured radii, but Fy(std) underestimates the absolute charge radii, especially with respect to the neutron-rich isotopes. FyðΔr; HFBÞ is the only functional which reproduces the correct direction of the OES pattern where measured values are available, although the staggering is overestimated somewhat, a feature which has also been observed in other isotopic chains [11,12,16,18]. The other two functionals tend to underestimate the staggering or even show reversed OES compared to the measured values, and also in the predictions for other odd-A isotopes.…”

“…This EDF was reoptimized within the Hartree-Fock-Bogoliubov (HFB) framework, resulting in the new FyðΔr; HFBÞ EDF [10,17]. It has been applied successfully to describe the charge radii of weakly bound proton-rich Ca nuclei [10]; to reproduce the kinks in the charge radii of Sn isotopes at the N ¼ 82 shell closure [7] and in the charge radii of Ag isotopes at N ¼ 50 [18]; to investigate the oddeven staggering (OES) in the charge radii of Cu isotopes [11]; and to reproduce the charge radii of K isotopes [12]. So far, all of these studies were performed close to shell closures, and thus in (mainly) spherical nuclei.…”