Recent shell-model results for exotic nuclei

Abstract

Abstract. We report on our recent advancement in the shell model and its applications to exotic nuclei, focusing on the shell evolution and large-scale calculations with the Monte Carlo shell model (MCSM). First, we test the validity of the monopole-based universal interaction (V MU ) as a shell-model interaction by performing large-scale shellmodel calculations in two different mass regions using effective interactions which partly comprise V MU . Those calculations are successful and provide a deeper insight into the shell evolution beyond the single-particle model, in particular showing that the evolution of the spin-orbit splitting due to the tensor force plays a decisive role in the structure of the neutron-rich N ∼ 28 region and antimony isotopes. Next, we give a brief overview of recent developments in MCSM, and show that it is applicable to exotic nuclei that involve many valence orbits. As an example of its applications to exotic nuclei, shape coexistence in 32 Mg is examined.

High-spin structures in Xe132 and Xe133 and evidence for isomers along the NVogt1, Siciliano2, Birkenbach3 et al. 2017Phys. Rev. C122120View full textAdd to dashboardCite

“…Consequently, the 940-keV transition is placed on top of the 2214-keV state. The line at 614 keV is identified as the decay of a (7,8,9 − ) state, previously observed in a β-decay study of 132m I [64]. Other lines visible in Fig.…”

“…The next even-even isotope 134 Xe exhibits a 10 130 Te the corresponding transition amounts to only 18 keV [17]. Backbending phenomena in the yrast bands were observed systematically in 122- 130 Xe, among others, visible in a reduced energy spacing between the 8 (7,8,9) − level at 2829 keV may be interpreted as the 8 − 1 state. Therefore, the 3155-keV state is most probably of spin 9 − 1 .…”

“…Three and four neutrons away from the N = 82 shell closure, the respective Xe isotopes have come within reach of advanced untruncated shell-model calculations. Several recently developed effective shell-model interactions [2][3][4][5][6][7] take aim toward a unified description of the 50 N, Z 82 region.…”

β− decay study of the Mn66−Fe66−CoStryjczyk1, Tsunoda2, Darby3 et al. 2018Phys. Rev. C171150View full textAdd to dashboardCite

“…Recent developments in theoretical models suggest that in order to reproduce the structure of exotic nuclei, the tensor force has to be included into the nuclear shell model potential [25]. Its monopole part influences the shell structure, which is known as shell evolution [26], and can lead to the erosion of the magic numbers [27][28][29] or changes in the single-particle shell ordering [30][31][32]. In the 68 Ni region, it is conjectured that shell evolution is responsible for a significant reduction of the energy gap between the 0f 7/2 and the 0f 5/2 proton shells, which gives a rise to creation of the different energy minima in the potential energy surface (PES) [21,[33][34][35].…”

Shell evolution beyondN=40:Cu69,71,73

“…As a consequence, energy gaps between single-particle orbitals can be reduced and new shell gaps may appear, altering the magic numbers that were first explained by Goeppert-Mayer in 1948 [1]. The interplay among central, spin-orbit, and tensor components of the effective nucleon-nucleon interaction can shift effective single-particle energies relative to each other as protons and neutrons fill certain orbitals near the Fermi surface in nuclei with large neutron excess [2][3][4][5][6][7][8][9][10][11]. This shell evolution far from stability has been experimentally observed in different mass regions: The magic numbers at N = 20 and 28 disappear for very proton deficient nuclei, and new magic numbers at N = 14, 16, 32, and 34 seem to appear [12][13][14][15][16][17][18][18][19][20][21][22][23].…”