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Register a new userCharge radii of potassium isotopes in the RMF(BCS)* approach
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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.
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We report on the measurement of optical isotope shifts for $^{38,39,42,44,46text{-}51}$K relative to $^{47}$K from which changes in the nuclear mean square charge radii across the N=28 shell closure are deduced. The investigation was carried out by bunched-beam collinear laser spectroscopy at the CERN-ISOLDE radioactive ion-beam facility. Mean square charge radii are now known from $^{37}$K to $^{51}$K, covering all $ u f_{7/2}$-shell as well as all $ u p_{3/2}$-shell nuclei. These measurements, in conjunction with those of Ca, Cr, Mn and Fe, provide a first insight into the $Z$ dependence of the evolution of nuclear size above the shell closure at N=28.
We compute the charge radii of even-mass neon and magnesium isotopes from neutron number N = 8 to the dripline. Our calculations are based on nucleon-nucleon and three-nucleon potentials from chiral effective field theory that include delta isobars. These potentials yield an accurate saturation point and symmetry energy of nuclear matter. We use the coupled-cluster method and start from an axially symmetric reference state. Binding energies and two-neutron separation energies largely agree with data and the dripline in neon is accurate. The computed charge radii have an estimated uncertainty of about 2-3% and are accurate for many isotopes where data exist. Finer details such as isotope shifts, however, are not accurately reproduced. Chiral potentials correctly yield the subshell closure at N = 14 and also a decrease in charge radii at N = 8 (observed in neon and predicted for magnesium). They yield a continued increase of charge radii as neutrons are added beyond N = 14 yet underestimate the large increase at N = 20 in magnesium.
Nuclear charge radii are sensitive probes of different aspects of the nucleon-nucleon interaction and the bulk properties of nuclear matter; thus, they provide a stringent test and challenge for nuclear theory. The calcium region has been of particular interest, as experimental evidence has suggested a new magic number at $N = 32$ [1-3], while the unexpectedly large increases in the charge radii [4,5] open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with $beta$-decay detection, we were able to extend the charge radii measurement of potassium ($Z =19$) isotopes up to the exotic $^{52}$K ($t_{1/2}$ = 110 ms), produced in minute quantities. Our work provides the first charge radii measurement beyond $N = 32$ in the region, revealing no signature of the magic character at this neutron number. The results are interpreted with two state-of-the-art nuclear theories. For the first time, a long sequence of isotopes could be calculated with coupled-cluster calculations based on newly developed nuclear interactions. The strong increase in the charge radii beyond $N = 28$ is not well captured by these calculations, but is well reproduced by Fayans nuclear density functional theory, which, however, overestimates the odd-even staggering effect. These findings highlight our limited understanding on the nuclear size of neutron-rich systems, and expose pressing problems that are present in some of the best current models of nuclear theory.
The systematic trend in charge radii along isotopic chain is of great interest due to its distinctive aspect at the nucleon-shell closure and the odd-even staggering (OES) behavior. In this work, the modified root mean square (rms) charge radius formula to phenomenally account for the formation of neutron-proton short-range correlations (np-SRCs) is firstly extended to study the heavier odd-$Z$ copper and indium isotopic chains. The parabolic-like shape of rms charge radii can be remarkably reproduced between two strong closure shells. In addition, the OES and abrupt changes in the slope of the rms charge radii across $N=50$ and $82$ shell closure are also identified evidently, but the odd-even oscillation is slightly overestimated for cooper isotopes. This means the np-SRCs play an indispensable role to determine the fine structures of nuclear charge radii along isotopic chain quantitatively.
Octet hyperon charge radii are calculated in a chiral constituent quark model including electromagnetic exchange currents between quarks. In impulse approximation one observes a decrease of the hyperon charge radii with increasing strangeness. This effect is reduced by exchange currents. Due to exchange currents, the charge radius of the negatively charged hyperons are close to the proton charge radius.
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