Isospin symmetry, a fundamental symmetry in nuclear physics arising from the identical behaviors of protons and neutrons. The symmetry violation is usually explained as isospin non-conserving (INC) forces and continuum effect. In experiments, plenty of efforts are made in mass and decay spectroscopy.
Hence, to extend this study into the heavier nuclei for the upper $fp$ shell, we propose to...
If pn pairing in the T=0 channel exists, one would expect a very collective $0^+ \rightarrow 1^+$ Gamow-Teller (GT) transition in the beta decay of a Z=N+2 nucleus into its N=Z counterpart [1], similar in strength to the super-allowed Fermi transition connecting the $0^+$ isobaric analog states. In a study performed at RIBF looking for these effects in the region around $A \sim 70$, we have...
A.Gadea, A.Algora, A.I.Morales, J.J. Valiente Dobon R.M. Perez Vidal, R.Illicachi, et al.
IFIC, CSIC-University of Valencia, Spain
A.Gottardo, G.de Angelis,et al.
INFN Laboratori Nazionali di Legnaro, Legnaro, Italy
A. Jungclaus, P. Sarriguren, et al.
Instituto de Estructura de la Materia, IEM-CSIC, Madrid, Spain
P.Doornenbal, et al.
RIBF, RIKEN, Japan
M.Górska, et al.
GSI-Darmstadt,...
Coherent motion of neutrons and protons in self-conjugate nuclei is a unique feature of nuclear many-body system. In the A=80 region, an emergence of large collectivity of the N=Z nuclei indicates large cross-shell excitation of protons and neutrons, predicting shape coexistence [1]. Experimentally a salient deviation of the correlation between B(E2; 2_1+ -> 0_1+) and R_4/2 of N=Z nuclides...
The concept of isospin was introduced by Heisenberg, inspired by the striking similarities between protons and neutrons in their behaviour under the strong interaction, playing a pivotal role in advancing our understanding of particle and nuclear physics. However, such symmetry is expected to be only approximate due to the mass difference between protons and neutrons, the Coulomb interaction,...
$^{100}$Sn is the last double magic N=Z nucleus that remains stable considering particle emission. Studying its beta decay is challenging and interesting [1-3], since it is very difficult to produce and the beta decay of $^{100}$Sn shows the lowest estimated Logft or the largest B(GT) (superallowed Gamow-Teller (GT) transition) in the entire nuclide chart. This decay also holds the key for a...
The discovery of the most neutron-deficient nuclei in the $^{100}$Sn region has opened possibilities for new and more precise spectroscopy experiments, especially in light of the increased primary beam intensity of $^{124}$Xe at RIKEN RIBF and a combined array of HPGe detectors for high $\gamma$-ray efficiency. The three major topics are presented below.
Shell model calculations showed a...
Investigation on the shell evolution far from stability is one of the core tasks of contemporary nuclear physics. Recently the N=82 shell gap at Z=74 obtained in the decay of new isotopes 160Os and 156W [1,2] confirmed theoretical predictions which show robust magicity of the next self-conjugate 164Pb.
Isomers are common in the proximity of N=82, such as the seniority and spin trap isomers in...
Neutron-deficient Pb nuclei feature unique shape coexistence with oblate, prolate and spherical shapes coexisting with few hundred keV in $^{186}$Pb. Not much is known in lighter Pb isotopes, with the spectroscopic knowledge vanishing at $^{178}$Pb. The structure of Pb isotopes with A<186 will allow one to understand the evolution of shape coexistence towards the lighter half of the N=82-126...
Islands of Inversion (IoI) are among the most intriguing phenomena in nuclear structure research. One of the least understood is the so-called $N=40$ IoI, centred around $^{64}$Cr ($Z=24$, $N=40$). Situated just below the spherical $^{68}$Ni ($Z=28$, $N=40$), the interplay between the negative-parity $pf$ neutron shell and the positive-parity $g_{9/2}$ and $d_{5/2}$ orbitals (spanning the...
The first spectroscopy of $^{78}$Ni suggested that the nucleus act as separation between a region. of sphericity and an island of deformation developing around N=50 for Z<28. In Fe isotopes, the spectroscopy with in-flight studies reached until $^{72}$Fe and $^{73}$Co (N=46), discovering an extension of the N=40 island of inversion towards the N=50 magic number. Also in $^{69,71}$Co low-lying...
In this contribution, I will present my personal view of the perspectives of decay spectroscopy experiments at RIBF in the years 2026/2027 in the region south-east of doubly-magic 132Sn. This view is based on past experience and theoretical expectation and considers isomeric decays, the observation of beta-delayed gamma radiation, as well as beta-decay half-lives.
The solar r-process abundance distribution has a small but distinct local maximum at A~160, known as the rare-earth abundance peak (REP). The REP formation is sensitive to both astrophysical and nuclear parameters. There are several different hypothesizes in the literature to understand the synthesis of these isotopes, but experimental data (nuclear masses, $\beta$-decay parameters and nuclear...
In the neutron-rich regions around N≈60 and N≈90, well-known sudden shape transitions occur. These transitions are evidenced by many aspects. From the view of ground-state energy, a pronounced kink in the trend of two-neutron separation energies ($S_{2n}$) and negative values of the neutron shell gap energies ($Δ_{2n}$) at N≈60 and N≈90. From the perspective of excited-state spectroscopy, the...
The neutron-rich rare-earth nuclei that lie mid-way between the proton shell-closures at Z=50,82 are expected to display a maximum of quadrupole deformation close to the double mid-shell N=104, Z=66. In addition, the appearance of deformed shell closures in this region, which depend on the interplay between single-particle and collective degrees of freedom, are important for understanding the...
We propose for systematic measurement of low lying states and beta decay half-life of Ho-Yb-Hf isotopes in unknown region N~114-120 to study i) sudden shape change expected in N~114-118 ii) half-life at the edge r-process nuclei near N~120.
The Ho-Hf region is one of the least studied in the nuclear chart, where only lifetime up to N=110 is known in the case of Yb. The region of Yb presents a...
The ground-state shape change as a function of the number of protons or neutrons is a typical Quantum Phase Transition (QPT) phenomenon. In the southwest of $^{208}$Pb, a shape transition from prolate to oblate, with a critical point around N=116, is proposed to occur as the neutron number increases (D. Cline, Annu. Rev. Nucl. Part. Sci. 36, 683 (1986)). To date, such evolution has been...
The availability, for higher intense beams at Riken, of a 100 pnA $^{238}$U, in combination with the increased efficiency of the $\gamma$-ray detection array compared to the previous EURICA campaign, opens the way to new experimental studies in the largely unexplored region of neutron-rich rare-earth nuclei. The structure of these nuclei is important from both nuclear astrophysics and nuclear...
We propose to measure the energies of the low-lying excited states of neutron-rich isotopes at N=126 202Os and below through decay spectroscopy of isomeric states. The primary motivation of the proposed experiment is to understand the shell evolution of π1h11/2 effective interactions. The evolution of the 1h11/2 orbital is crucial to study i) possible existence of Z=76 subshell closure and...
The nuclear structure and β-decay properties of neutron-rich nuclei near the N=126 shell closure are important for understanding nuclear interaction in heavy nuclei and astrophysical processes. Sensitivity studies of r-process nucleosynthesis have shown that uncertainties in the predicted abundance around the A~195 peak depend considerably on the accuracy of β-decay rates of neutron-rich...
