Irradiations of bismuth samples with thermal and epithermal neutrons have been performed for a comparison of activation to the ${}^{210g}\mathrm{Bi}$ ground state and to the ${}^{210m}\mathrm{Bi}$ metastable state. The bismuth irradiations were conducted at the Soreq IRR1 research reactor at a near-core location with integrated neutron flux of approximately $2\times {10}^{18}\mathrm{neutrons}/\mathrm{c}{\mathrm{m}}^2$ and a gold cadmium ratio of 3.1. Two nearly identical bismuth samples were irradiated, one without and one with a cadmium shield, to enable a comparison between thermal and epithermal neutron capture cross sections. Subsequent gamma spectrometry indicates nearly equal levels of activation to the ground and to the metastable states of ${}^{210}\mathrm{Bi}$, both with thermal and epithermal neutrons. Absolute thermal cross sections and resonant integrals were deduced by including previously reported bismuth activation measurements performed conjointly with gold foil activation for normalization. A comparison of the present results with existing data is presented. It is argued that the bismuth resonances lie in the neutron energy range relevant for stellar temperatures, and therefore the neutron capture cross section ratio $\left({\sigma }_g/{\sigma }_m\right)$ measured for the epithermal neutrons is relevant also for stellar ${}^{210}\mathrm{Bi}$ production. This is of importance since bismuth lies at the end of the chain for the s‐process reaction for nucleosynthesis in stars. Precise knowledge of bismuth activation to the ${}^{210m}\mathrm{Bi}$ metastable state is also vital for the planning of GEN-IV reactors given the 3-million-yr half-life of ${}^{210m}\mathrm{Bi}$.

Background: Stars with an initial mass of $\approx 7$–11 solar masses form degenerate oxygen-neon cores following carbon burning. Electron captures in such cores can trigger runaway oxygen burning, resulting in either a collapse or a thermonuclear explosion. Previous work constrained the contribution of the forbidden $0_{\text{g.s.}}^{+}\to 2_{\text{g.s.}}^{+}$ transition to the ${}^{20}\mathrm{Ne}(e^{-},{\nu }_e){}^{20}\mathrm{F}$ rate and discussed its significance for the evolution of the core.

Purpose: We provide a detailed description of the formalism used in previous work and apply it to two further forbidden transitions that are relevant to degenerate oxygen-neon cores: the $4_{\text{g.s.}}^{+}\to 2_1^{+}$ transition in ${}^{24}\mathrm{Na}(e^{-},{\nu }_e){}^{24}\mathrm{Ne}$ and the $5/2_{\text{g.s.}}^{+}\to 1/2_{\text{g.s.}}^{+}$ transition in ${}^{27}\mathrm{Al}(e^{-},{\nu }_e){}^{27}\mathrm{Mg}$.

Method: The relevant nuclear matrix elements are determined through shell model calculations and constraints from the conserved vector current (CVC) theory. We then investigate the astrophysical impact using the stellar evolution code mesa (Modules for Experiment in Stellar Astrophysics) and through timescale arguments.

Results: In the relevant temperature range, the forbidden transitions substantially reduce the threshold densities for ${}^{24}\mathrm{Na}(e^{-},{\nu }_e){}^{24}\mathrm{Ne}$ and ${}^{27}\mathrm{Al}(e^{-},{\nu }_e){}^{27}\mathrm{Mg}$. In the mesa models, ${}^{24}\mathrm{Na}(e^{-},{\nu }_e){}^{24}\mathrm{Ne}$ now occurs immediately following the onset of ${}^{24}\mathrm{Mg}(e^{-},{\nu }_e){}^{24}\mathrm{Na}$. The impact on the overall evolution is uncertain; this is due to known difficulties in accounting for convective instabilities triggered by the $A=24$ electron captures. The transition between ${}^{27}\mathrm{Al}$ and ${}^{27}\mathrm{Mg}$ may have a minor effect on the early evolution but is unlikely to affect the outcome.

Conclusions: The studied transitions should be included when calculating weak interaction rates between ${}^{24}\mathrm{Na}$ and ${}^{24}\mathrm{Ne}$ for temperatures ${log}_{10}\left(T\left[\text{K}\right]\right)\lesssim 8.5$ and between ${}^{27}\mathrm{Al}$ and ${}^{27}\mathrm{Mg}$ for ${log}_{10}\left(T\left[\text{K}\right]\right)\lesssim 8.8$.

We propose a new approach to determine the strength of the charge symmetry breaking (CSB) term in the framework of nuclear density functional theory. It is shown that once ab initio calculations are available including accurate description of isospin symmetry breaking terms in medium and heavy nuclei, the mass difference of mirror nuclei as well as the neutron-skin thickness of doubly-closed-shell nuclei can be used to constrain the strength of the CSB interaction with an uncertainty less than 6%, separately from other isospin symmetry breaking forces. This method opens a new vista of ab initio nuclear energy density functionals.

The dipole strength of the nuclide ${}^{76}\mathrm{Ge}$ was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.8 and 12.3 MeV delivered by the electron linear accelerator of high brilliance and high brightness (ELBE). We identified 210 levels up to an excitation energy of 9.4 MeV and assigned spin $J$ = 1 to most of them. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical $\gamma$-ray cascades. The photoabsorption cross section up to the neutron-separation energy was determined and is compared with predictions of the statistical reaction model. The derived photon strength function is compared with results of experiments using other reactions.

Background: The $\alpha$ particles emitted from excited states of ${}^{12}\mathrm{C}$ could be utilized for cancer treatment and the method is called proton boron capture therapy (PBCT). The $\alpha$ particles are created by a clinical proton beam on the ${}^{11}\mathrm{B}$ target. The ${}^{11}\mathrm{B}+p$ threshold corresponds to the excitation energy of $16.0\mathrm{MeV}$ in ${}^{12}\mathrm{C}$, where the excited states decay by emitting $\alpha$ particles.

Purpose: For the nuclear structure side, whether the ground state of ${}^{11}\mathrm{B}$ contains the seeds of the cluster states is a crucial question. It has been known that one of the noncentral interactions, the spin-orbit interaction, plays a role in nuclear systems of washing out the $\alpha$ clusters; it works as a driving force to stabilize the symmetry of the $jj$-coupling shell model. It is of special importance to show the persistence of $\alpha +\alpha +t$ cluster configuration in the ground state of ${}^{11}\mathrm{B}$.

Methods: In addition to the basis states with cluster configurations, we include their breaking effects by employing the antisymmetrized quasicluster model. The cluster states and shell-model states are treated on the same footing and are coupled.

Results: The inclusion of the breaking effect of $\alpha +\alpha +t$ cluster structure is found to contribute to the lowering of the ground-state energy by about $2\mathrm{MeV}$, and cluster structure is slightly broken. The third $3/2^{-}$ state has been suggested as a cluster state both theoretically and experimentally, and we confirmed the well-developed clustering.

Conclusions: The ground state of ${}^{11}\mathrm{B}$ can be considered as a seed of the cluster states; it still keeps enough component of $\alpha +\alpha +t$ cluster. Assuming the typical three-$\alpha$-cluster state of ${}^{12}\mathrm{C}$ as an equilateral triangular configuration with the relative distances of 3–4 fm, the ground state of ${}^{11}\mathrm{B}$ is found to have a certain squared overlap with such state when a proton approaches.

A detailed study of total, Coulomb, and nuclear breakup cross sections dependence on the projectile ground-state binding energy ${\varepsilon }_b$ is presented by considering the ${}^8\mathrm{Li}+{}^{12}\mathrm{C}$ and ${}^8\mathrm{Li}+{}^{208}\mathrm{Pb}$ breakup reactions. To this end, apart from the experimental one-neutron separation energy of ${}^8\mathrm{Li}$ nucleus $({\varepsilon }_b=2.03\mathrm{MeV})$, lower values of ${\varepsilon }_b$ down to ${\varepsilon }_b=0.01\mathrm{MeV}$, are also being considered. It is shown that all breakup processes become peripheral as ${\varepsilon }_b\to 0.01\mathrm{MeV}$, which is understood as due to the well-known large spacial extension of ground-state wave functions associated to weakly bound projectiles. The Coulomb breakup cross section is found to be more strongly dependent on ${\varepsilon }_b$ than the nuclear breakup cross section, such that the Coulomb breakup becomes more significant as ${\varepsilon }_b$ decreases, even in a naturally nuclear-dominated reaction. This is mainly due to the long-range nature of the Coulomb forces, leading to a direct dependence of the Coulomb breakup on the electromagnetic transition matrix. It is also highlighted the fact that the nuclear absorption plays a minor role for small binding when the breakup becomes more peripheral.

Laser resonance ionization spectroscopy was performed on the rare einsteinium isotopes ${}^{253-255}\mathrm{Es}$ at the RISIKO mass separator in Mainz. With low sample sizes ranging down to femtograms, the prominent 352 nm-ground-state transition was measured in all three einsteinium isotopes, and four additional ground-state transitions were measured in ${}^{254}\mathrm{Es}$. Hyperfine-structure analysis resulted in assigned spin values of $I\left({}^{254}\mathrm{Es}\right)=7$ and $I\left({}^{255}\mathrm{Es}\right)=7/2$. From the extracted coupling constants, nuclear magnetic dipole moments of ${\mu }_I\left({}^{254}\mathrm{Es}\right)=3.42\left(7\right){\mu }_N$ and ${\mu }_I\left({}^{255}\mathrm{Es}\right)=4.14\left(10\right){\mu }_N$ as well as spectroscopic electric quadrupole moments of $Q_s\left({}^{254}\mathrm{Es}\right)=9.6\left(1.2\right)e\mathrm{b}$ and $Q_s\left({}^{255}\mathrm{Es}\right)=5.1\left(1.7\right)e\mathrm{b}$ were derived. Our value for ${}^{254}\mathrm{Es}$ deviates from the value of $|{\mu }_I\left({}^{254}\mathrm{Es}\right)|=4.35\left(41\right){\mu }_N$ extracted from the angular anisotropy of $\alpha$-radiation emitted by ${}^{254}\mathrm{Es}$.

Radii of nuclear charge distributions carry information about the strong and electromagnetic forces acting inside the atomic nucleus. Whereas the global behavior of nuclear charge radii is governed by the bulk properties of nuclear matter, their local trends are affected by quantum motion of proton and neutron nuclear constituents. The measured differential charge radii $\delta \langle r_c^2\rangle$ between neutron numbers $N=28$ and $N=40$ exhibit a universal pattern as a function of $n=N\text{–}28$ that is independent of the atomic number. Here we analyze this remarkable behavior in even-even nuclei from calcium to zinc using two state-of-the-art theories based on quantified nuclear interactions: the ab initio coupled cluster theory and nuclear density functional theory. Both theories reproduce the smooth rise of differential charge radii and their weak dependence on the atomic number. By considering a large set of isotopic chains, we show that this trend can be captured by just two parameters: the slope and curvature of $\delta \langle r_c^2\rangle \left(n\right)$. We demonstrate that these parameters show appreciable model dependence, and the statistical analysis indicates that they are not correlated with any single model property, i.e., they are impacted by both bulk nuclear properties as well as shell structure.

We report on $\gamma$-ray spectroscopy of low-lying excited states in the neutron-rich ${}^{94,95,96}\mathrm{Kr}$ isotopes measured as part of the “Shell Evolution And Search for Two-plus energies At RIBF” (SEASTAR) campaign at the RIKEN Radioactive Isotope Beam Factory. Excited yrast and non-yrast states were observed, and half-lives extracted via geant4 simulations. In ${}^{94,96}\mathrm{Kr}$ candidates for the $3_1^{-}$ state were identified. For ${}^{95}\mathrm{Kr}$, the prompt SEASTAR data were combined with delayed spectroscopic data measured with the EURICA array to observe transitions on top of the known ${(7/2)}^{+}$ isomer at a level energy of 195.5(3) keV. The comparison of the new experimental results with five-dimensional collective Hamiltonian (5DCH) and mapped interacting boson model (IBM) calculations, both using the Gogny D1M interaction, could suggest oblate-prolate shape coexistence already in ${}^{96}\mathrm{Kr}$.

The structure of nuclei around the neutron-rich nucleus ${}^{132}\mathrm{Sn}$ is of particular interest due to the vicinity of the $Z=50$ and $N=82$ shell closures and the $r$-process nucleosynthetic path. Four states in ${}^{131}\mathrm{Sn}$ with a strong single-particle-like component have previously been studied via the ($d,p$) reaction, with limited excitation energy resolution. The ${}^{130}\mathrm{Sn}({}^9\mathrm{Be},{}^8\mathrm{Be}){}^{131}\mathrm{Sn}$ and ${}^{130}\mathrm{Sn}({}^{13}\mathrm{C},{}^{12}\mathrm{C}){}^{131}\mathrm{Sn}$ single-neutron transfer reactions were performed in inverse kinematics at the Holifield Radioactive Ion Beam Facility using particle-$\gamma$ coincidence spectroscopy. The uncertainties in the energies of the single-particle-like states have been reduced by more than an order of magnitude using the energies of $\gamma$ rays. The previous tentative $J^{\pi }$ values have been confirmed. Decays from high-spin states in ${}^{131}\mathrm{Sn}$ have been observed following transfer on the isomeric component of the ${}^{130}\mathrm{Sn}$ beam. The improved energies and confirmed spin-parities of the $p$-wave states important to the $r$-process lead to direct-semidirect cross sections for neutron capture on the ground state of ${}^{130}\mathrm{Sn}$ at 30 keV that are in agreement with previous analyses. A similar assessment of the impact of neutron-transfer on the isomer would require significant nuclear structure and reaction theory input. There are few measurements of transfer reaction on isomers, and this is the first on an isomer in the ${}^{132}\mathrm{Sn}$ region.

There is strong evidence for the formation of small droplets of quark-gluon plasma in $p/d/{}^3\mathrm{He}+\mathrm{Au}$ collisions at the Relativistic Heavy Ion Collider (RHIC) and in $p+p/\mathrm{Pb}$ collisions at the Large Hadron Collider. In particular, the analysis of data at RHIC for different geometries obtained by varying the projectile size and shape has proved insightful. In the present analysis, we find excellent agreement with the previously published PHENIX at RHIC results on elliptical and triangular flow with an independent analysis via the two-particle correlation method, which has quite different systematic uncertainties and an independent code base. In addition, the results are extended to other detector combinations with different kinematic (pseudorapidity) coverage. These results provide additional constraints on contributions from nonflow and longitudinal decorrelations.

We perform a systemical investigation of the low-lying doubly heavy dibaryon systems with strange $S=0$, isospin $I=0$, 1, 2, and the angular momentum $J=0$, 1, 2, 3 in the quark delocalization color screening model. We find the effect of channel-coupling cannot be neglected in the study of the multi-quark systems. Several bound systems are obtained. They are the doubly charm dibaryon systems with $IJ=00$, $IJ=01$, and $IJ=02$, and the corresponding energies are 4590, 4720, and 4764 MeV, respectively; and the doubly bottom dibaryon systems with $IJ=00$, $IJ=02$, and $IJ=13$, and the corresponding energies are $11219$, $11416$, and $11633$ MeV, respectively. Besides, six resonance states are obtained, which are $IJ=00N{\mathrm{\Xi }}_{cc}$ and $N{\mathrm{\Xi }}_{bb}$ with resonance masses of 4730 and 11411 MeV respectively, $IJ=11N{\mathrm{\Xi }}_{cc}^{*}$ and $N{\mathrm{\Xi }}_{bb}^{*}$ with resonance masses of 4775 and 11432 MeV respectively, and $IJ=12{\mathrm{\Sigma }}_c{\mathrm{\Sigma }}_c^{*}$ and ${\mathrm{\Sigma }}_b{\mathrm{\Sigma }}_b^{*}$ with resonance masses of 4935 and 11626 MeV respectively. All these heavy dibaryons are worth searching for in experiments, although it will be a challenging work.

Differences in the charge radii of mirror nuclei have been recently suggested to contain information on the slope of the symmetry energy $L$. To test this hypothesis, we perform statistical correlation analysis using quantified energy density functionals that are consistent with our previous knowledge on global nuclear observables such as binding energies and charge radii. We conclude that the difference in charge radii between a mirror pair, $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$, is an inferior isovector indicator compared to other observables, such at the neutron skin or electric dipole polarizability ${\alpha }_{\mathrm{D}}$. In particular, this quantity correlates poorly with both the neutron skin and $L$. We demonstrate that $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$ is influenced by pairing correlations in the presence of low-lying proton continuum in the proton-rich mirror-partner nucleus. Considering the large theoretical uncertainties on $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$, we conclude that the precise data on mirror charge radii cannot provide a stringent constraint on $L$.

Background: ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ is one of the key reactions of nuclear astrophysics, playing a role in various stellar processes and influencing energy generation of stars, stellar evolution, and nucleosynthesis. For a reliable reaction rate calculation, the low-energy cross section of ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ must be known with high accuracy. Owing to the unmeasurable low cross sections, theoretical calculations are unavoidable.

Purpose: High-precision experimental cross section data are needed in a wide energy range in order to provide the necessary basis for low-energy extrapolations. In the present work, the total ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ cross section was measured with a method complementary to the available data sets.

Method: The cross section was measured with activation, based on the detection of the annihilation radiation following the ${\beta }^{+}$ decay of the reaction product ${}^{15}\mathrm{O}$. This method, which provides directly the astrophysically important total cross section, was never used for the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ cross section measurement in the studied energy range.

Results: The nonresonant cross section was measured between 550 and 1400 keV center-of-mass energies with total uncertainty of about 10%. The results were compared with literature data using an $R$-matrix analysis. It is found that the cross sections measured in this work are in acceptable agreement with the two recent measurements only if the weak transitions—not measured in those works—are included.

Conclusions: The present data set, being largely independent from the other available data, can be used to constrain the extrapolated cross sections to astrophysical energies and helps to make the astrophysical model calculations more reliable.

Response functions are at the heart of any comparison of theory with experiment in studies of the nuclear dynamics with electroweak probes. Calculations performed in the laboratory frame often suffer from center of mass contaminations that need to be removed. By confining the system in a harmonic oscillator, we derive a set of analytical formulas to subtract the center of mass effects from calculations of response functions and associated sum rules. After a general analytical derivation, we first deal specifically with the longitudinal response function appearing in electron scattering and provide expressions for the center of mass correcting functions. Next, we present a proof of principle study for the case of the electric dipole sum rules in a two-body problem with a numerical implementation of our formalism. These steps pave the way to applying the proposed method to heavier nuclei in the future.

We establish a definite parametrization of $R$-matrix theory, which is complete and invariant. Compared to the traditional parametrization of Wigner and Eisenbud, our parametrization has the major advantage of having no arbitrary boundary condition $B_c$, and of being constituted of scattering matrix poles ${\mathcal{E}}_{\lambda }$, which are physical quantities and hence invariant with the choice of arbitrary channel radii $a_c$. Moreover, being the poles of the scattering matrix, the definite levels ${\mathcal{E}}_{\lambda }$ correspond exactly to the nuclear resonances. Our definite parametrization is also global and complete, meaning a finite number of definite parameters—the same number as the Wigner and Eisenbud ones, minus the boundary conditions—can fully describe the scattering matrix on the whole complex plane [it is thus not a local description restricted to an energy window as the previous Windowed Multipole Representation of Ducru et al., Phys. Rev. C 103, 064610 (2021)]. These benefits come at the cost of requiring all parameters to now be complex numbers without an explicit set of constraints, which significantly complicates their direct nuclear data evaluation. We show that our parametrization also gives rise to shadow poles, though we prove they can be ignored and still completely reconstruct the scattering matrix with all its poles, and thus describe nuclear cross sections exactly. This means our parametrization only requires as many scattering matrix poles ${\mathcal{E}}_{\lambda }$ as there are Wigner-Eisenbud resonance levels $E_{\lambda }$, thereby establishing a one-to-one correspondence between the traditional Wigner-Eisenbud and our definite parametrization of $R$-matrix theory. Remarkably, we show these same cross sections can also be obtained using the shadow poles instead of the principal poles. We observe evidence of these phenomena in the spin-parity group $J^{\pi }=1/2^{(-)}$ of xenon isotope ${}^{134}\mathrm{Xe}$.

We analyze recent data on a long series of high-spin states in ${}^{208}\mathrm{Pb}$ with a self-consistent phonon-coupling model for nuclear excitations based on the Skyrme functionals. The model is the renormalized time-blocking approximation which takes the coherent one-particle–one-hole states of the random-phase approximation (RPA) as starting point to develop more complex configurations beyond RPA. To the best of our knowledge, this is the first investigation of high spin states in ${}^{208}\mathrm{Pb}$ using self-consistent nuclear models. The interesting point here is that complex configurations are compulsory to describe the upper end of the long spin series at all. The data thus provide an ideal testing ground for phonon-coupling models as they give direct access to complex configurations. We find that standard Skyrme functionals which perform well in ground state properties and giant resonance excitations deliver at once an agreeable description of these high spin states.

Background: Lying at the lower edge of the “island of inversion,” neutron-rich fluorine isotopes (${}^{29\text{–}31}\mathrm{F}$) provide a curious case to study the configuration mixing in this part of the nuclear landscape. Recent studies have suggested that a prospective two-neutron halo in the dripline nucleus ${}^{31}\mathrm{F}$ could be linked to the occupancy of the $pf$ intruder configurations.

Purpose: Focusing on configuration mixing, matter radii, and neutron-neutron ($nn$) correlations in the ground state of ${}^{31}\mathrm{F}$, we explore various scenarios to analyze its possible halo nature as well as the low-lying electric dipole ($E1$) response within a three-body approach.

Method: We use an analytical, transformed harmonic oscillator basis under the aegis of a hyperspherical formalism to construct the ground-state three-body wave function of ${}^{31}\mathrm{F}$. The $nn$ interaction is defined by the Gogny-Pires-Tourreil potential that includes the central, spin-orbit, and tensor terms, while the different two-body potentials to describe the core $+n$ subsystems are constrained by the different possible scenarios considered.

Results: The ${}^{31}\mathrm{F}$ ground-state configuration mixing and its matter radius are computed for different choices of the ${}^{30}\mathrm{F}$ structure coupled to the valence neutron. The admixture of $p_{3/2}$, $d_{3/2}$, and $f_{7/2}$ components is found to play an important role, favoring the dominance of inverted configurations with dineutron spreads for two-neutron halo formation. The increase in matter radius with respect to the core radius, $\mathrm{\Delta }r\gtrsim$ 0.30 fm and the dipole distributions along with the integrated $\mathrm{B}\left(E1\right)$ strengths of $⩾2.6$ $e^2{\mathrm{fm}}^2$ are large enough to be compatible with other two-neutron halo nuclei.

Conclusion: Three-body results for ${}^{31}\mathrm{F}$ indicate a large spatial extension in its ground state due to the inversion of the energy levels of the normal shell model scheme. The increase is augmented by and is proportional to the extent of the $p_{3/2}$ component in the wave function. Additionally, the enhanced dipole distributions and large $\mathrm{B}\left(E1\right)$ strengths all point to the two-neutron halo character of ${}^{31}\mathrm{F}$.

The structural properties of even-even nuclei along the $\beta$-stability line are systematically analyzed and investigated by means of our improved potential-energy-surface (PES) approach. The equilibrium deformations obtained from the PES minima are compared with available experimental data and other theoretical results. From a different viewpoint, taking the nuclei on the stability line as footholds, we systematically present two-nucleon separation energies and half-lives in the corresponding isotopic chains. Very regular laws can be seen, especially below $Z=84$. The observed trends and anomalous behavior are briefly discussed. The energy difference between theory and experiment for the binding energies and two-nucleon separation energies indicates that the improved PES calculations with our fitting macroscopic model parameters are relatively in better agreement with experiments. Based on the systematic law of two-nucleon separation energies, the bound limit of even-even nuclei is crudely estimated along the stability line.