The Gamow-Teller giant resonance is one of the most basic collective modes in nuclei and belongs to the spin-isospin (pion) channel. This mode has long been studied for stable nuclei to clarify a variety of nuclear properties such as the behavior of spin-isospin residual interactions, nuclear weak responses. Recently, with the advent of RI falicities worldwide, the study of GTR has been...
Gamow-Teller (GT) strengths in medium and heavy nuclei in the giant-resonance region are suppressed compared to the Ikeda sum rule [1,2]. GT strengths in low-lying states in sd-shell and pf-shell nuclei, for example, have also been found to be suppressed: the quenching factors for the axial-vector coupling, $q_{A}=g_{A}^{eff}/g_{A}^{free}$, are $\sim$0.77 and $\sim$0.74 for $sd$-shell [3] and...
Motivated by the experimental and theoretical interest on the Isovector Monopole Resonance, I will present a theoretical study of the charge-exchange and non-charge exchange Isovector Monopole Resonances in 48Ca, 90Zr and 208Pb calculated within the RPA approach. I will focus on their excitation energy and sum rules and discuss the possibility to relate them with the ground state properties of...
The nuclear matter radius is one of the fundamental physical quantities, and the interaction cross section measurement is a method used to deduce this radius. Measurement of interaction cross sections using the transmission method achieves an accuracy of 0.5% with statistics from only 10^5 to 10^6 particles, owing to the large cross section and the ability to use thick targets. This...
Nuclear collective excitation such as giant resonances provides valuable information on understanding the structure of finite nuclei and the equation of state for infinite nuclear matter. The quasiparticle random-phase approximation (QRPA) is a suitable theoretical framework that is capable of describing collective excitation as a superposition of the two-quasiparticle excitation, but it...
The generator coordinate method (GCM) has been a well-known method to describe nuclear collective motions [1]. In GCM, one a priori specifies collective degrees of freedom (collective coordinates), such as nuclear deformations, and superposes many Slater determinants (SDs) within the selected collective subspace. However, there always exists arbitrariness in this approach in the choice of...
Nuclear magnetic properties provide valuable insights into nuclear structure. In particular, the magnetic dipole moment is sensitive to how much the nucleus is dominated by the single-particle picture. Reproducing magnetic dipole moments has been one of the major challenges in nuclear ab initio theory. With the valence-space in-medium similarity renormalization group (VS-IMSRG), one of the ab...
The magnetic dipole moment and the electric quadrupole moment are the nuclear moments that provide us with key information about the proton and neutron configurations in a nucleus and the shape of a nucleus, respectively. In the study of nuclear structure through the measurement of the nuclear moments, a technique to produce spin orientation of RI beams has played important roles. In the...
Recent spectroscopic measurements in neutron-rich $N=40$ nuclei towards $^{60}$Ca give an insight into shell structure in this region [1]. Large-scale shell model calculations [2] predicted a sizable collectivity in $^{60}$Ca and the island of inversion extended to $^{60}$Ca.
In this contribution, we will present the results of low-lying states in $N=40$ nuclei by employing the...
One of the long-standing subjects of nuclear physics is the exotic structure of nuclei located far from the $\beta$-stability line. Particularly, neutron-rich nuclei around $N\sim20$ have been attracting significant attention, and intensive experimental and theoretical studies have been performed to reveal their nuclear structures. Various structures have been predicted, as a result of the...
The study of the heaviest elements remains a compelling scientific endeavor. By investigation of nuclei in the trans-fermium region, we can learn about the quasi-particle structure, pairing correlations, and excitation modes in these nuclei. Berkeley Lab scientists have led several recent experiments to study the excited level structure of nuclei in this region through prompt and delayed...
We have developed the KEK Isotope Separation System (KISS) [1] at RIKEN to study the nuclear structure of the nuclei in the vicinity of neutron magic number $N =$ 126 from the astrophysical interest. These neutron-rich nuclei have been produced by using multinucleon transfer reactions [2] with the combinations of the low-energy $^{136}$Xe beam and the production targets of W, Ir, and Pt.
At...
Intruder orbitals in the shell structure play important roles in the existence and disappearance of the magic numbers and the nuclear shape. Magicity loss of $N=8$ in light beryllium nuclei is one of the attractive subject from this viewpoint.
The $^{12}$Be has low-lying $0^+$ isomeric state at 2.2~MeV due to the narrow gap at $N=8$ caused by the intruder orbital from $sd$-shell[1] and its...
The shapes of nuclei are essentially determined by the single-particle shell structures. Semiclassical periodic orbit theory (POT) gives us a very powerful tool in describing the origin of gross shell structures and their properties. The POT formula expresses the quantum level density in terms of the contributions of classical periodic orbits (POs). The major gross shell structure is...
Recent works using direct reactions and the solenoidal-spectrometer technique have revealed insights into the single-particle structure of weakly bound nuclei. Using CERN’s HIE-ISOLDE facility and the ISOLDE Solenoidal Spectrometer, the single-neutron strengths and energies of the $1f_{7/2}$, $2p_{3/2}$, $2p_{1/2}$, $0h_{9/2}$, $1f_{5/2}$, and $0i_{13/2}$ valence neutron orbitals outside of...
As representing the shell structure in certain regions, the pseudo-spin symmetry (PSS) has been found helpful in describing some characteristic structures of nuclei. In short, the PSS is the near degeneracy of single-particle (s.p.) orbitals with $\mathit{\Delta}j=1$ and $\mathit{\Delta}\ell=2$. It has been argued since the late 1990s that the PSS is a relativistic symmetry, as the s.p....
We would like to present the effect of including two-particle two-hole (2p-2h) states in nuclear resonances. Configuration spaces of 2p-2h are known to be important to describe a spreading width of nuclear resonances. Recently, our group pointed out that its effect is also important to reproduce high-energy particle emission rates. To understand this phenomena comprehensively, it is necessary...
The isospin symmetry of atomic nuclei is broken due to the Coulomb interaction and the isospin symmetry breaking part of the nuclear interaction. The former gives the dominant contribution to the isospin symmetry breaking of atomic nuclei, and the latter is a small part of the whole; however, it sometimes gives important contributions to nuclear properties, such as the mass difference of...
The equation of state (EOS) of nuclear matter is important not only for understanding the properties and dynamics of nuclei but also for explaining the astrophysical phenomena, such as neutron stars merger and supernova explosions. Research on the EOS from experimental nuclear physics attempts to determine the behavior near saturation density and symmetric nuclear matter from nuclear...
Neutron-rich isotopes have unique structural properties, such as the neutron halo where weakly bound neutrons are spatially extended from the core. Two-neutron halo nuclei such as $^6$He, $^{11}$Li, and $^{19}$B are especially interesting subject since they are Borromean nuclei. A Borromean nucleus is a bound three-body system where any of the two-body subsystems are unbound. Recent Coulomb...
Search for the Island of Stability (IoS) has been one of the most attractive problems in modern nuclear physics. IoS is predicted to exist in the neutron-rich vicinity near Z = 114, N = 184, the Super Heavy Element (SHE) within are anticipated to have a lifetime longer than a year while the lifetime of SHE synthesized in the lab are on the order of ms. The huge enhancement in the stability is...
I will present a theoretical evaluation of coupled-spin entanglement in the two-proton (2p) radioactive emission [1]. For this purpose, a time-dependent three-body model is utilized [2].
Spin entanglement has been evaluated in terms of the coupled-spin correlation S_{CHSH} for the two fermions. Here this S_{CHSH} is so-called Clauser-Horne-Shimony-Holt (CHSH) indicator. For the two protons...
We have performed a Coulomb excitation experiment of $\rm ^{58}Ti$ and
determined its $B(\rm E2)$ value to study the evolution of collectivity in
the Ti isotopes towards $N=40$.
The neutron number $N=40$ is a magic
number in the harmonic oscillator model.
However, the magic character is not observed in most nuclei because of the
narrowing of the shell gap due to spin-orbit...
Spin-zero pairing correlation in finite nuclei produces a systematic difference between the ground-state energies of even and odd-mass nuclei. We customarily use the odd-even mass staggering when discussing pairing correlation, but it is difficult to precisely calculate the energies of odd-mass ground states, especially in the nuclear density functional theory (DFT). Another physical...
We report on the kinematically complete measurement of the Coulomb breakup of the two-neutron halo nucleus $^{14}$Be on Pb at 220 MeV/nucleon at SAMURAI at RIBF. The previous study [1] showed significantly large E1 excitation of $^{14}$Be at low excitation energies, which was indicative of the revelation of the soft E1 excitation for halo nuclei, while the statistics was low and the...
We used the Relativistic Hartree-Fock theory to calculate the equation of state (EOS) of spin-polarized matter, where the spins of nucleons are biased either up or down. Similar to the slope parameter of the isospin-symmetry energy in spin unpolarized matter, we define the “spin slope parameter” of the spin-symmetry energy to characterize the variation of the energy as the spin polarization is...
The rapid spherical to prolate shape transition at N = 60 in the mid-shell region around Z = 40 has been evidenced from diverse experiments [1-5], and the shape evolution for more neutron-rich nuclei has been of interest because of the emergence of the triaxial degree of freedom. Theoretical predictions suggested further phase transitions such as a shape transition to oblate spheroid [6-8], a...
Determining the equation of state for nuclear matter is one of the primary goals in nuclear physics, and is essential for understanding the macroscopic properties of nuclear matter in equilibrium states in both finite systems (nuclei) and infinite systems (neutron stars). The objective of our study is to derive the density-dependent term L for the symmetry energy, focusing on the symmetry...
In some nuclei, a phenomenon called double beta decay, in which two nucleons simultaneously undergo beta decay, is known to occur rarely. In this case, two neutrinos are emitted. Neutrinos may be Majorana particles, which do not distinguish between particles and antiparticles among Fermi particles. In that case, double beta decay without neutrino emission ($0\nu\beta\beta$) may occur. If the...
One of the primary goals of nuclear physics is to achieve a unified understanding of baryon-baryon interactions based on flavor symmetry and its breaking. Charge symmetry breaking (CSB) represents a part of the flavor symmetry that is violated by nuclear forces, leading to differences in neutron-neutron and proton-proton interactions, as well as in neutron-Lambda and proton-Lambda...
In this study, we discuss the shell structure at $N=32$ and $34$, newly recognized magic numbers in neutron-rich nuclei, in the context of deformation toward $N=40$ based on nuclear mass implications. Mass measurements of isotopes $^{55}$Sc, $^{55-58}$Ti, and $^{55-59}$V were conducted during the first commissioning of the ZD-MRTOF system at the RIBF/RIKEN under the SLOWRI project. The newly...
The parameter set of many kinds of density functionals are designed not only to reproduce the basic properties of finite nuclei but also to satisfy the saturation properties of nuclear matter. Consequently, calculations using density functionals can describe experimental data in various mass regions. However, the mean-field calculations using the functionals miss some many-body...
The energy density functional method provides a systematic approach to analyzing nuclear properties across the entire nuclear chart. We have performed calculations for nuclei from the proton drip line to the neutron drip line, including superheavy nuclei. Using the HFBTHO program (Axially deformed solution of the Skyrme-Hartree–Fock–Bogoliubov equations using the transformed harmonic...
Very neutron-rich isotopes, including 28−32Ne, in the vicinity of N = 20 are known to exhibit ground states dominated by fp-shell intruder configurations: the "island of inversion." Systematics for the Ne-isotopic chain suggest that such configurations may be in strong competition with normal shell-model configurations in the ground state of 29Ne. A determination of the structure of 29Ne is...
The issue of tritium water caused by the Fukushima nuclear power plant disaster has become a social problem. In this presentation, the tritium transmutation reaction to 3He is analyzed and reported from the viewpoint of ab-initio calculation of nuclear force.
We present a statistical analysis of nuclear low-lying states within the framework of multireference covariant density functional theory (MR-CDFT) using a relativistic point-coupling energy density functional (EDF). This study is made possible by the newly developed subspace-projected (SP)-CDFT, where the wave functions of nuclear low-lying states for target EDF parameter sets are expanded in...
We have investigated the nuclear structure properties of the medium-heavy nucleus like Cd isotopes in the framework of the nuclear shell model.
We have used the ab initio shell model Hamiltonian from the in-medium Similarity Renormalization Group (IMSRG) approach.
Here, two types of IMSRG approaches have been used, namely IMSRG(2) and a factorized approximation of IMSRG(3).
In this work,...
The study of isomeric states in nuclei is crucial for understanding the nuclear structure, as these states often exhibit structures significantly different from their ground states. The neutron-rich nucleus $^{12}$Be has an isomeric $0^{+}_{2}$ at $E_x = 2.3$ MeV with a half-life of 230 ns (see level diagram in the upper right of Fig. 1). This state undergoes deexcitation via an E2 transition...
Shape coexistence has been observed in nuclei located close to the “Island of Inversion”, where the disappearance of the magic number N = 20 is well known. This nuclear structure is one of the important topics that has been extensively studied both experimentally and theoretically. Our group has systematically investigated nuclear structure in this mass region, focusing on the isotopes of Mg...
The charge density distributions of nuclei, ρ(r), are the best determined by elastic electron scattering, and those of the stable nuclei that have been studied so far have played an essential role in revealing their internal structure.
Recently, the 4th-order moment of the charge density distribution, $
Exploring the nuclear shell structure of neutron-rich $N=50$ nuclei is one of the most interesting and mysterious phenomena in nuclear physics, and it has become the forefront of both experimental and theoretical research in recent years. We have constructed the shell model Hamiltonian in the $\pi(fp)$-$\nu(sdg)$ model space based on {\it ab-initio} approach VS-IMSRG($3{\rm f}_2$) with...
Can alpha particles be the basic building blocks of atomic nuclei? The conventional mean-field picture with nucleons as basic degrees of freedom is considered to dominate, particularly in the ground state of the doubly magic nucleus 16O. On the other hand, alpha cluster theories have predicted their existence in the ground state of 16O [1, 2, 3]. Recently, proton-induced alpha-knockout...
The doubly-magic nucleus $^{132}$Sn and its surrounding nuclei are expected to provide crucial insights into the nuclear shell model structure. In order to extend the nuclear structure studies for low lying states so far, here we carried out the measurement of nuclear magnetic moments of $^{130}$Sn and $^{132}$Sn, by focusing on their higher spin isomeric states. The $^{130}$Sn and $^{132}$Sn...
Density functional theory, widely adopted in nuclear physics, incorporates many-body correlations by expressing the interaction between nucleons constituting a nucleus using a density-dependent Hamiltonian. In addition to two-body nuclear forces, three-body nuclear forces are known to be important in the interaction between nucleons, and density functional theories of the Skyrme and Gogny...
The interaction cross section is a key physical quantity for deducing nuclear radii and plays an essential role in understanding nuclear structure, particularly for neutron-rich isotopes. In this study, we measured the interaction cross sections of Al, Si, and P isotopes near Z=14 to investigate their mass-number dependence and explore nuclear deformation effects.
The experiment was carried...
The interaction cross section is one of the physical quantities that can be used to deduce the nuclear radius, and its measurement contributes to the understanding of the structure of unstable nuclei. While charge radii provide information about the proton distribution, deriving nuclear matter radii from interaction cross sections allows us to gain additional insights into the neutron...
In the 1950s, Bohr and Mottelson established the picture that most heavy nuclei deform into a prolate shape consisting of one long axis and two short axes of equal length.
However, the recent theoretical calculation by T. Otsuka et al.[1] indicates that these nuclei prefer a triaxial shape, with all three axes having different lengths. Additionally, the presence of excited states due to...
Nuclear Mass and Fission-Fragment Studies based on the
FRDM and FRLDM Models.
Peter Möller
Department of Mathematical Physics, Lund Institute of Technology,
Box 118, SE - 22100 Lund, Sweden
The latest FRDM and FRLDM global mass models were finalized in 2012 and pub-
lished in 2016[1]. We investigate how the masses in the tables agree with subse-
quently measured masses. The FRLDM model...
Nuclear systems show two kinds of natures, i.e., cluster and mean field aspects, providing rich phenomena in nuclei. The cluster aspect is found in ground state correlations, which induce nuclear deformations and polygon shapes such as the triangle of $^{12}$C and tetrahedron of $^{16}$O. In the excited states, it contributes to low-lying monopole and dipole excitations. Proton and alpha...
Atomic nuclei are finite quantum many-body systems consisting of protons and neutrons. Their structures are governed by the strong interactions. Extensive experimental and theoretical studies over the past decades have yielded sophisticated phenomenological realistic nucleon-nucleon, as well as (semi-phenomenological) chiral two- and three-nucleon interactions. However, it is still not...
At the limit of stability, atomic nuclei can exhibit unique structure due to the proximity to the particle-
decay threshold. In particular, if orbitals near the Fermi surface have low angular momenta, they can
induce spatially extended wave functions for valence neutrons, forming nuclear halo. In light p and psd
shells, halo nuclei have so far served as a benchmark for understanding of...
Astro-$\nu$ interactions are studied by inverse $\beta$ decays and $\nu$-properties beynod the standard model are studied by neutrinoless double beta decays (0$\nu\beta\beta$). The $\beta$ and $\beta\beta$ nuclear matrix elements (NMES) consist mainly of the axial-vector spin ($\sigma$) isospin($\tau$) components, The delta-isobar ($\Delta$) resonance excited by the quark $\tau\sigma$...
The concepts of triaxiality and -softness are introduced based on the collective liquid model. Pertaining signatures are the quadrupole shape invariants derived from the E2 matrix elements, the energy ratios and the staggering of the energies of the band . Microscopic Triaxial Projected Shell Model (TPSM) calculations have been carried out for nine nuclei with extended sets of E2 matrix...
The Xe nuclei with mass A < 120 are perfectly placed to study the octupole correlations phenomena. For these nuclei, the presence of octupole driving h11/2 and d5/2 orbitals near the Fermi surface make them suitable to exhibit octupole correlation. Other than Xe nuclei such octupole correlations have also been reported in several other isotopes of Cs and Ba having N < 70. In previous high spin...
The production of a superheavy element in a fusion heavy-ion reaction schematically proceeds through the three stages: (i) the two colliding nuclei overcome the Coulomb repulsion and come in contact, (ii) the contact configuration evolves into a compact shape, (iii) the fused nucleus cools down by neutron evaporation. In the present presentation the second step is described in a new method...
Loosely bound nuclei are currently at the centre of interest in low-energy nuclear physics. The deeper understanding of their properties provided by the shell model for open quantum systems changes the comprehension of many phenomena and offers new horizons for spectroscopic studies of nuclei
from the driplines to the valley of $\beta$-stability, for states in the vicinity and above the...
In studies of nuclear physics during the last decades, the area of nuclides in the nuclear chart available for experiments increases drastically because of developments of rare isotope beam facilities as well as of experimental technique. Systematic studies of nuclear structure are performed as a function of numbers of protons and neutrons, which show evolution of structures, exotic phenomena...
Covariant density functional theory is applied on a three-dimensional lattice in a microscopic and fully self-consistent manner, without imposing any symmetry restrictions [1], to investigate the superheavy nucleus $^{286}$No. Our findings reveal that the ground state exhibits a distinct non-axial octupole shape, which coexists with a tetrahedral isomeric state. The energy difference between...
It is known that nuclear deformation plays an important role in inducing the halo structure in neutron-rich nuclei by mixing several angular momentum components. While previous theoretical studies on this problem in the literature assume axially symmetric deformation, we here consider non-axially symmetric deformations. With triaxial deformation, the Ω quantum number is admixed in a...
The two-proton radioactivity (2p decay), where two protons are simultaneously emitted
during nuclear decay, was theoretically predicted over 60 years ago[1]. In the early 2000s,
2p decay was discovered in very proton-rich nuclei such as 45Fe and 48Ni [2, 3]. The en-
ergy level structure and one- and two-proton separation energies (Sp, S2p) are essential to
evaluate the two-proton emission...
The focus of this work is neutron-rich Fe and Mn isotopes with N~40, which lie within an Island of Inversion approximately centered at 64Cr. Here, a quenching of the N=40 sub-shell gap allows multi-particle multi-hole excitations and deformation to develop in the ground-state configurations of nuclei in the region. Limited spectroscopic information has been collected so far in the...
The structure of nuclei far from the stability line is a central theme of research in Nuclear Physics. Key to this program has been the worldwide development of advanced radioactive beam facilities and novel detector systems, which provide the tools needed to produce and study these exotic nuclei.
One of the intellectual drivers guiding current experimental and theoretical research concerns...
