The 24th International Spin Symposium

Contribution ID: 168

Type: Parallel Session keynote talk (by invitation only)

Spin contents of Na isotopes towards driplines
Wednesday, 20 October 2021 12:00 (25 minutes)
The structure evolution of neutron-rich isotopes provides with many intriguing facets. Recently, we presented[1] how such evolution occurs in F-Ne-Na-Mg isotopes up to their neutron driplines, by using an ab initio effective nucleon-nucleon (N N ) interaction derived from the chiral Effective Field Theory of QCD [2]. In thispresentation, we shall report some features of the spin contents obtained quite recently by extending thisapproach. These features are focused on because of the main interest of the conference. We thus discuss themagnetic moments of Na isotopes up to their dripline, in agreement with experimental values [3].
The wave functions used in this work can produce another nice agreement with experiment for the charge/matterradii and the quadrupole moments, as well as the ground-state energies [1]. The dripline is located at 39 Na,
being most likely consistent with experiment [1,4].
One of the remarkable findings is that the magnetic moments of the ground states of Na isotopes up to 31 Na
can be well described by free spin g-factors (gs ). On the other hand, it appears that the orbital g-factors (gl )are changed from the free values by an isovector shift of 0.2. Such an isovector shift of the orbital g-factors isquite usual, and is ascribed to the meson effect which can be needed independently of the nuclear structure
calculation. On the other side, the spin quenching has been considered to be due to the 2p2h excitations
across the relevant magic gap (core polarization or configuration mixing), which are explicitly included, inour calculation, between the sd and pf shells thanks to the present ab initio effective N N interaction capableof describing such cross-shell excitations. We note that only the present interaction may have this capability
among various ab initio interactions proposed so far, due to its derivation by the EKK method [5]. It is ofinterest to examine predicted values for Na isotopes beyond 31 Na.
The predicted magnetic moments of exotic Na isotopes indeed point to strongly deformed shapes, as expectedin the scenario presented in Ref. [1]. The neutron spin contents of exotic Na isotopes are quite small up to thedripline nucleus. The proton spin contents are more sizable, but differ from those in the single-particle picture.
Thus, the exotic Na isotopes are expected to be a very interesting domain in the nuclear chart, including theirmagnetic properties.
[1] N. Tsunoda, T. Otsuka, K. Takayanagi, {\it et al.}, Nature {\bf 587}, 66 (2020).
[2] R. Machleidt and D. R. Entem, Phys. Rep. {\bf 503}, 1 (2011).
[3] National Nuclear Data Center’s ‘Evaluated Nuclear Structure Data File’(http://www.nndc.bnl.gov/ensdf/).
[4] D. S. Ahn, {\it et al.}, Phys. Rev. Lett. {\bf 123}, 212501 (2019).
[5] N. Tsunoda, K. Takayanagi, M. Hjorth-Jensen, and T. Otsuka, Phys. Rev. C {\bf 89}, 024313 (2014).

Primary author: OTSUKA, Takaharu (University of Tokyo)
Co-author: Dr SHIMIZU, Noritaka (University of Tokyo)
Presenter: OTSUKA, Takaharu (University of Tokyo)
Session Classification: Spin in Nuclear Reactions and Nuclei
Track Classification: Parallel Sessions: Spin in Nuclear Reactions and Nuclei