Conveners
NS2022 Plenary: Light Nuclei I
- Carl Svensson (Department of Physics, University of Guelph, N1G 2W1 Guelph, Canada)
NS2022 Plenary: Heavy Nuclei I
- Jacklyn Gates (LBL)
NS2022 Plenary: Shapes and Collectivity I
- Marco Siciliano (ANL)
NS2022 Plenary: Shells/Magicity I
- Mark Caprio (University of Notre Dame)
NS2022 Plenary: Heavy Elements II
- Walid Younes (LLNL)
NS2022 Plenary: Islands of Inversion
- D. Bazin (NSCL, Michigan State University)
NS2022 Plenary: Shapes and Collectivity
- Peter Bender (University of Massachusetts Lowell)
NS2022 Plenary: Statistical Structure and Astrophysics
- Dorthea Gjestvang
NS2022 Plenary: Mirrors and Proton-Rich Nuclei
- A. Rogers (University of Massachusetts Lowell, USA)
NS2022 Plenary: Lasers
- Kyle Leach (Colorado School of Mines)
NS2022 Plenary: Light Nuclei II
- D.G. Jenkins (Dept of Physics, Univ of York)
NS2022 Plenary: Shapes and Collectivity III
- Gordon Ball (TRIUMF)
NS2022 Plenary: Shells and Magicity II
- Corina Andreoiu (Simon Fraser University)
NS2022 Plenary: Fundamental Symmetries
- M. Wiedeking (iThemba LABS)
NS2022 Plenary: Shapes and Collectivity IV
- Yang Sun
NS2022 Plenary: Closing Session
- Heather Crawford
NS2022 Plenary: New Facilities
- Andrew Boston
The search for chargeless nuclei consisting only of neutrons has been a long-lasting challenge in nuclear physics, dating about 50 years back. The tetraneutron, in particular, has attracted a lot of experimental and theoretical attention. Theoretical models agree that nuclear forces do not bind four neutrons together, but struggle to handle the resonance case. On the other hand, no solid...
The nucleus $^8$He is the most neutron-rich nucleus known. Its structure, consisting of a $^4$He core surrounded by four neutrons makes it an ideal case to study phenomena in highly neutron-proton asymmetric systems and neutron correlations at the nuclear surface.
An experiment studying proton inelastic scattering of $^8$He has been carried out at the IRIS setup at ISAC-II at TRIUMF. It...
Inspired by the recent results of Ref. [1] showing strong evidence for a deformed 8He nucleus, we present a study of the structure of the odd-A 7He and 9He isotopes in the rotational model. While the ab initio calculations predict an oblate shape, in this work we consider two cases corresponding to an oblate and a prolate core with deformation |ε2| ≈ 0.38 as inferred in [1].
A comparison...
The very/super-heavy nuclei area is a unique laboratory in the nuclear chart for the fundamental study of the atomic nucleus since excitation and decay modes are governed by the competition between the short-range strong nuclear interaction, long-range Coulomb repulsion, surface effects and the properties of individual quasiparticle states. For such studies, a wide scientific program has been...
Spectroscopy of Trans-fermium Nuclei Using the Argonne Gas-Filled Analyzer
D. Seweryniak,$^1$ T. Huang,$^{1,2}$ K. Auranen,$^{1,11}$ A.D. Ayangeakaa,$^{1,12}$ B.B. Back,$^1$ P. Bender,$^3$
M.P. Carpenter,$^1$ P. Chowdhury,$^3$ R.M. Clark,$^4$ P. Copp,$^1$ Z. Favier,$^{10}$ K. Hauschild,$^8$ X.-T. He,$^5$
R.D. Herzberg,$^6$ D. Ho,$^3$ H. Jayatissa,$^1$ T.L. Khoo,$^1$ F.G. Kondev,$^1$...
Experiments on the heaviest nuclei are addressing the fundamental issue of the maximum limits of nuclear mass and charge. The difficulty of producing such exotic nuclei, however, creates an inherent challenge for elucidating the detailed structure of these extreme nuclear systems. By contrast, nuclei in the vicinity of $Z=100$ and $N=152$ may be studied in much greater detail, and yet they...
The interaction between electrons and the atomic nucleus introduces an avenue for laser spectroscopy measurements to probe changes in the nuclear structure across an isotopic chain, providing a nuclear model-independent method to determine fundamental properties such as the spin, the mean-squared charge radius, and nuclear moments. Laser spectroscopic techniques have been historically...
Shape coexistence occurs when the potential energy of the nucleus is characterized by local minima for different shapes. Excited states in the secondary minimum may become a isomeric if the potential barrier separating the secondary minimum from the ground-state minimum is sufficiently pronounced. The first examples of such shape isomers were observed in the 1960s, as fission isomers in the...
Performing shell model calculations for heavy, deformed nuclei has been a challenging problem in nuclear physics. State-of-the-art many-body techniques, such as angular momentum projection (AMP) [1] and generator coordinate method (GCM) [2], are required. In this talk, we present two new developments of shell models with their potential applications. Both developments are benefited by the...
Isotopes of zirconium (Zr) with semi-magic atomic number $40$ represent one of the most interesting cases of shape evolution in nuclei. The collective behavior of Zr nuclides is very much suppressed at neutron number $50$, where $^{90}$Zr exhibits properties of a doubly-magic nucleus. On the other hand, a sudden onset of nuclear deformation appears at $N = 40$ and $60$ due to the strong...
The stable to neutron-rich isotopes of germanium are a critical testing ground for nuclear models due to their complex and rapidly changing nuclear structure. The even-A 72–78Ge isotopes exhibit triaxial deformation, and the presence shape coexistence has also been suggested in 72Ge [1]. A transition from prolate to oblate shapes occurs at 70Ge [2], and another region of triaxiality has...
The long chain of Sn isotopes is a formidable testing ground for nuclear models studying the evolution of shell structure and interplay between pairing and quadrupole correlations. A transition from superfluid nuclei at midshell to spherical nuclei is also expected approaching the neutron shell closures at N = 50, where the seniority scheme can be adopted to describe the energy spectra....
A systematic global investigation of differential charge radii has been performed within the covariant density functional framework for the first time [1,2,3]. Theoretical results obtained with conventional covariant energy density functionals and separable pairing interaction are compared with experimental differential charge radii in the regions of the nuclear chart in which available...
Gamma-ray spectroscopy is a versatile tool which can be used to study the decay of the excited fragments produced in the complex process of nuclear fission. Gamma ray coincidence and relative time information can give important information on both the nuclear structure of exotic
neutron-rich nuclei and the fission process itself. Recent results from the nu-Ball hybrid gamma-ray spectrometer...
Even after decades of research, still very little is known about the fundamental nuclear or chemical properties of the heaviest elements. These elements do not exist naturally on earth, so experimental studies are incredibly challenging. Theoretical work has already predicted where the "island of stability" should be and were the periodic table of the elements should end, but these regimes are...
Long-lived K-isomers at high angular momenta in very neutron-rich deformed Hf (Z=72) nuclei have been predicted for decades, but their spectroscopy has remained elusive as they are difficult to populate. Not only are these nuclei interesting from a nuclear structure perspective, but they also border the r-process pathway, and thus their $\beta$-decays are of considerable relevance for our...
$^{212}$Po has two-protons and neutrons outside the doubly-magic nucleus $^{208}$Pb and it may be assumed that the nuclear structure can be well described within the shell-model. But various experimental properties, such as the short-lived ground state, are better described by an $\alpha$-clustering model. The B(E2) values of the decays of the low-lying yrast states are an important finger...
Spin-Orbital (SO) splitting generates the magic numbers when N>20 but the SO potential itself is not well constrained. Calculations based on Density Function Theory (DFT) predict a “proton bubble” in the $^{34}$Si nucleus, together with a sudden reduction of the SO-splitting between the 0p$_{1/2}$ and 0p$_{3/2}$ orbitals in $^{35}$Si relative to the same orbitals in $^{37}$S. A similar “proton...
The ISOLDE Solenoidal Spectrometer (ISS) is a new magnetic spectrometer that has been developed to study direct reactions with exotic beams produced at the ISOLDE facility, CERN. ISS was fully commissioned during 2021 and the first physics campaign took place using a new on-axis position-sensitive silicon array, constructed by the University of Liverpool, mounted inside the 4T former-MRI...
Direct reactions represent a unique mechanism to investigate the nuclear-structure properties and the nature of single-particle states of nuclei along shell closures. In this contribution, the $^{46}$Ar($^3$He, d)$^{47}$K proton-transfer reaction is proposed for the study of properties of the ground state of the radioactive neutron-rich $^{46}$Ar isotope. The interest behind this isotope stems...
The $\beta$-decays of $^{36}$Mg and $^{36}$Al have been studied at The National Superconducting Cyclotron Laboratory (NSCL) in order to extract the half-lives of the parent nuclei and reveal the nuclear structure of the decaying descendants. Neutron-rich $^{36}$Mg and $^{36}$Al were produced at the NSCL's Coupled Cyclotron Facility via projectile fragmentation of a $^{48}$Ca beam of energy 140...
Neutron-rich nuclei with mass around A=100 exhibit a rapid change of nuclear deformation. A sudden onset of deformation is observed for the Sr and Zr isotopes at neutron number N=60. For Mo and Ru isotopes the transition is more gradual and the shape becomes increasingly triaxial. Nuclear shapes in this wider mass region were studied by measuring lifetimes of excited states in an experiment at...
Results from recent experiments studying nuclei in the $^{78}$Ni region suggest that the $N=50$ shell closure persists, in agreement with state-of-the-art shell-model calculations. However, how collectivity manifests and evolves in this region of the Segrè chart is still an open question, particularly concerning phenomena such as vibrational modes, axial shape asymmetry (triaxiality) and shape...
Atomic nuclei close to 72Kr are expected to feature enhanced octupole correlations since both proton and neutron single-particle levels are close to the Fermi surface, which differ by Δj = Δl = 3. Previous QRPA calculations predicted only small electric octupole strength in this mass region, which is at odds with the experimental systematics gathered in the stable Kr isotopes and...
The self-conjugate N=Z nuclei have been an intriguing subject for a long time due to their peculiar characteristics for proton-neutron correlations and quadrupole-quadrupole interactions. In particular, a significant shape change has been anticipated among the medium-mass nuclides. The structure of N=Z molybdenum (Z=42) isotope, 84Mo, attracts attention in this viewpoint since the theoretical...
Significant progress has been made in the study of photon strength functions (PSF) over the last few years. The nature of the so-called low-energy enhancement of the PSF is being unraveled. In addition, PSF and nuclear level density (NLD) measurements have provided unprecedented constraints on nucleosynthesis processes through much improved neutron capture cross sections. The successful...
Approximately half of the elements heavier than iron are thought to be produced in the r process. Recent insights into the astrophysical site of this critical process highlight the need for experimental data on short-lived neutron-rich nuclei. R-process nucleosynthesis sensitivity studies show that the final abundance distributions of r-process nuclei are greatly impacted by β-decay...
The γ -ray emission from the nuclei 62,64 Fe following Coulomb excitation at bombarding energy of 400-
440 AMeV was measured with special focus on E1 transitions in the energy region 4-8 MeV. The
unstable neutron-rich nuclei 62,64 Fe were produced at the FAIR-GSI laboratories and selected with the
FRS spectrometer. The γ decay was detected with AGATA HPGE tracking array. From the measured γ...
Neutron-capture cross sections play a vital role in our understanding of heavy element nucleosynthesis. In astrophysical processes such as the intermediate neutron-capture process and rapid neutron-capture process, element formation occurs in neutron-rich environments and involves short-lived isotopes for which capture cross sections cannot be measured via direct techniques. Instead reaction...
Unlike any other physical system the nucleus represents a unique dual quantum many-body system. Its constituents, protons and neutrons, are assumed to be identical, except for their electric charge. They can be seen as two representations of the nucleon, with isospin components t$_z$ = ±1/2 for neutrons and protons, respectively. Under the assumption of charge independence of the strong...
Different parameterizations of Skyrme energy density functionals show large variations in the stiffness of the neutron equation of state (EOS), making extrapolations to higher densities uncertain [bro00]. It has been shown that the difference in mirror pair charge radii is correlated with the L parameter, which is the slope of the symmetry energy in the nuclear EOS [bro17]. By placing...
The discovery of the new proton emitter 116La, 23 neutrons away from stable 139La, will be reported. 116La nuclei were synthesised in the fusion-evaporation reactions at the University of Jyväskylä Accelerator Center and identified via their proton radioactivity using the MARA recoil mass spectrometer. Comparisons of the measured proton energy (E= 718 keV) and half-life (T1/2 = 50 +-22ms) with...
Atomic nuclei having (almost) the same number of neutrons (N) and protons (Z) attract a great deal of attention due to the various interesting physics phenomena associated with these systems. During the past few decades the focus has been on the isospin symmetry properties of the nuclei located around the N = Z line. More recently, owing to the development of radioactive ion beam...
Electromagnetic properties of short-lived radionuclides represent sensitive probes for the structural evolution of atomic nuclei far away from stability. Experimentally, these can be accessed, for instance, by laser spectroscopy in which measurements of the atomic hyperfine structure reveal electromagnetic moments and charge radii of nuclear ground states and long-lived isomers.
Due...
The use of high resolution optical measurements of the atomic structure is at the forefront of modern subatomic physics. Laser spectroscopy provides model-independent nuclear data of nuclear spins, moments and charge radii across long chains of isotopes~\cite{Campbell}. This allows the study of the evolution of nuclear observables versus particle number to probe shape deformation,...
In this contribution, we present measurements of the nuclear magnetic dipole moments and nuclear electric quadrupole moments of the 113-131In isotope chain, performed using the Collinear Resonance Laser Spectroscopy experiment at ISOLDE, CERN.
We show that the electromagnetic properties of the neutron-rich indium isotopes significantly differ at N = 82 compared to N < 82, despite the single...
Beta-delayed neutron emission ($\beta$-n) plays a vital role in shaping the elemental abundance distribution in the $r$-process via modifying the decay path back to stability and by contributing significantly to the neutron flux after freeze-out [1]. Modeling the $\beta$-n process requires a good model of the beta-strength functions and of the neutron emission mechanism. Statistical...
Thermonuclear reactions between light nuclei play an important role in explaining the origin and evolution of our universe, but are generally very difficult or even impossible to measure at the astrophysically relevant energies of tens to hundreds of keVs due to the hindering effect of Coulomb repulsion. As a result, they are almost always estimated by extrapolation from higher-energy...
Short-range correlations (SRC) in nuclei - nucleon pairs with large relative momentum, but small total momentum - arise from the strong, short-distance NN interaction. These are important components of the nuclear ground state, but it is difficult to study their contributions in low-energy reactions. GeV-scale electron scattering measurements have been used to study scattering from SRCs in...
We report the result of a study of the isomeric state in $^{16}$N via the $^{16}$N^{g,m}($d$,$^3$He)$^{15}$C reaction in inverse kinematics at 11.8 MeV/u using the HELIOS spectrometer. The radioactive 16N beam, with a 24(2)% isomer component, was produced using the ATLAS RAISOR in-flight separator at ANL. The simultaneous measurements of the reactions provided the most direct and reliable...
Ab initio nuclear theory, for which the only input is the inter-nucleon interaction, can provide a deeper understanding of the origins of nuclear collective behavior. In no-core shell model (NCSM) calculations of p-shell nuclei, rotational bands with vastly different structure and deformation appear within the same nucleus (shape coexistence). To gain insight into the underlying symmetries...
The 'island of inversion' centered on $^{32}$Mg is characterized by ground state configurations with an inverted ordering of $sd$ and $pf$ (intruder) neutron orbitals due to nuclear deformation and nucleon-nucleon interactions. For neutron rich $sd$ shell nuclei outside of the 'island of inversion', similar configurations incorporating the neutron $pf$ shell occur in levels with high...
Mass measurement facilities are extremely important in furthering our understanding of nuclear structure away from the valley of stability, including aiding in the search for collective behaviors in exotic nuclei. TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) is among the world’s premier precision trapping facilities, with the newly added Multiple-Reflection Time-of-Flight Mass...
Detailed spectroscopy of neutron-rich, deformed rare-earth nuclei is of broad interest for nuclear structure. The structure of nuclei midshell in both proton and neutron number helps to understand the evolution of deformed subshell gaps and the interplay of single-particle and collective degrees of freedom in these nuclei. High-statistics decay spectroscopy of $^{160}$Gd resulting from the...
Experimental and theoretical studies of the germanium isotopes point increasingly toward exotic combinations of nuclear-structure effects, with indications of triaxiality, configuration mixing, and shape coexistence. Studies of the $E0$ strengths, which can provide a direct measure of the amount of configuration mixing, are lacking along the Ge chain. Thus, an experimental determination of...
Nuclei away from the line of stability have been found to demonstrate behavior that is inconsistent with the traditional magic numbers of the spherical shell model. This has led to the concept of the evolution of nuclear shell structure in exotic nuclei, and the neutron-rich Ca isotopes are a key testing ground of these theories; there have been conflicting results from various experiments as...
New experimental $\beta$-decay half-lives, $\beta$-delayed neutron emission probabilities (P$_{xn}$), and $\gamma$ ray for neutron-rich nuclei in the $A\approx$90-100 region are of interest for nuclear structure, industrial applications, and astrophysics. The scarce experimental data in very the neutron-rich regions involved in the $r$-process nucleosynthesis is the main source of uncertainty...
$^{78}$Ni is one of the few radioactive doubly-magic nuclei on the nuclear landscape [1]. It has a large neutron-to-proton ratio and engages in beta-delayed neutron and gamma emissions. Decays of Cu isotopes with significant neutron excess provide a laboratory to study such doubly-magic nuclei. The nuclear shell structure of $^{79}$Cu (N=50; Z=29) is highly similar to the one of $^{78}$Ni...
The $\beta$ decay of the neutron-rich $^{134}$In and $^{135}$In was investigated experimentally with the aim of providing new insights into the nuclear structure of the tin isotopes above $N=82$. Better understanding of exotic nuclides from the $^{132}$Sn region is required for accurate modeling of the rapid neutron capture nucleosynthesis process ($r$ process), due to the $A \approx 130$ peak...
The recoiling daughter nucleus in weak nuclear decay processes ($\beta$ or EC decay) is a unique probe for a wide range of nuclear structure properties and BSM physics scenarios. In particular, precision measurements of the recoil can be used to access model-independent information on the neutrino mass, the $\beta$-$\nu$ angular correlation, precise excited- and ground-state energies, and...
Precision molecular experiments provide a unique tool for the measurement of electroweak nuclear properties and searches for physics beyond the Standard Model (SM). Compared to atoms, certain molecules can offer more than eleven orders of magnitude enhanced sensitivity to violations of fundamental symmetries, enabling precision tests of the SM and the possibility to probe energy scales beyond...
The weak interaction of the Standard Model is well-described by a vector-axial vector, or ‘V-A’, structure, which reproduces both maximal parity violation and left-handed neutrinos in beta- decay. However, there is no first-principles reason that other the interactions, such as scalar (S) or tensor (T), may not be present. To search for possible tensor contributions to the weak interaction we...
The experimental evidence of the seniority conservation is a direct evidence of the validity of the short-range pairing interaction, with far-reaching implications for nuclear structure in the validity of the BCS theory and therefore of the quasiparticle representation of the atomic nucleus [1]. In theory, this symmetry is preserved up to $j<=7/2$ and, contradictory experimental results exist...
The heaviest $T_z = 0$ doubly-magic nucleus, $^{100}$Sn, and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction. From Cd to Te, many common features and phenomena have been observed experimentally along the isotopic chains, leading to theoretical studies devoted to a more general and comprehensive study of the region.
Having only two...
The first results from CLARION2-TRINITY, a new charged-particle and HPGe array are presented: Coulomb excitation of $^{49}$Ti. Ti-49 can be treated as a neutron hole plus semimagic $^{50}$Ti core within the particle-core coupling scheme. Reduced electric quadrupole transition probabilities, or $B(E2)$ strengths, for the $2^{+} \otimes f_{7/2}$ multiplet members and candidate $p_{3/2}$ state...
The many-body Hamiltonian that describes atomic nuclei is exceedingly complex and remains unknown. Thus, the lowest energy state cannot be calculated directly from first principles for heavy nuclei. This has lead to many theoretical endeavors to predict the ground-state properties based on the mean-field concept. In a novel and alternative approach, we show that it is possible to predict...
Nuclides near the neutron drip line are the frontier in nuclear structure experiment and theory. But full configuration-interaction (FCI) calculations of such nuclides, which provide detailed spectra, can be computationally prohibitive. Instead, we approximate FCI calculations by embedding so-called ``beyond mean-field'' methods in a shell-model framework. Previous work showed that...
There are two fundamental kinds of excitation modes in the atomic nucleus: collective and single-particle
excitations. So far, most of the theoretical effort has focused on the study of the former and the latter has
been mostly treated by using the quasiparticle spectrum of neighboring nuclei [1] or the equal-filling
approximation [2]. However, these approaches explicitly neglect time-odd...
Owing to its very low excitation energy the isomer of thorium-229 has been proposed as a candidate for a possible future frequency standard, a nuclear clock and is expected to outperform the current atomic clocks [1,2]. Currently, the best values of the excitation energy are 8.28(17) eV and 8.10(17) eV [3,4]. These were measured using two different techniques where the population of the isomer...
