The ${}^{23}\mathrm{Na}(p,\gamma ){}^{24}\mathrm{Mg}$ reaction plays an important role in the nucleosynthesis of elements in the hot bottom burning environment of asymptotic giant branch stars by providing a breakout path from the NeNa cycle to the MgAl cycle. At temperatures above $\approx 0.06$ GK, the underlying nuclear reaction contributions to the rate are primarily narrow resonances, but at lower temperatures direct and broad resonance tail contributions come to dominate. While there have been recent studies to improve the uncertainties associated with these narrow resonances, little attention has been paid to the nonresonant component. In this work, experimental measurements are reported over the energy range from 0.5 and 1.05 MeV proton beam energy, with a focus on studying the off-resonance region of the cross section. Several transitions were observed where two broad resonances dominate the energy range and whose low energy tails contribute strongly to the low-energy, nonresonant, cross section. In addition, a clear signature of direct capture has been observed for the first time in the ${}^{23}\mathrm{Na}(p,\gamma ){}^{24}\mathrm{Mg}$ reaction.

The $2\nu \beta \beta$ decay from the ground to the first excited $2^{+}$ state is considered for eight nuclei where experimental data are available. The transition amplitude is calculated with a projected spherical single-particle basis, a fully renormalized proton-neutron quasiparticle random-phase approximation (pnQRPA) for the Gamow-Teller (GT) dipole transition operator and a renormalized QRPA for charge conserving quadrupole operators. Also for the transition operator the first-order boson expansion expression is employed. Using the phase space integral corresponding to the transition $0^{+}\to 2^{+}$ and the GT transition amplitude, the process half-life is readily obtained. The single-${\beta }^{\mp }$ transition strengths are studied as function of the energies of the fully renormalized pnQRPA with the gauge symmetry restored. The single-$\beta$ transition operators are used to calculate the ${log}_{10}ft$ values for the electron capture of the intermediate odd-odd nucleus to the mother nucleus as well as for the ${\beta }^{-}$ transition to the daughter nucleus. For the final state in the daughter nucleus the $B\left(E2\right)$ values for the transition $2^{+}\to 0^{+}$ and the half-life of the electromagnetic decaying state are calculated. The Ikeda sum rule for the mother nucleus is satisfied. The mentioned results are compared with the corresponding available data and a reasonable agreement is shown. The gauge projection quenches the half-life in the case of ${}^{150}\mathrm{Nd}, {}^{116}\mathrm{Cd}$, and ${}^{100}\mathrm{Mo}$ and enhances it for the remaining considered nuclei. Keeping the same parameters for the model Hamiltonian the ground to ground double-$\beta$ transition is also treated and a good agreement with the existing data is obtained.

Whether quantum chromodynamics (QCD) exhibits a phase transition at finite temperature and density is an open question. It is important for hydrodynamic modeling of heavy ion collisions and neutron-star mergers. Lattice QCD simulations have definitively shown that the transition from hadrons to quarks and gluons is a crossover when the baryon chemical potential is zero or small. We combine the parametric scaling equation of state, usually associated with the three-dimensional Ising model, with a background equation of state based on a smooth crossover from hadrons to quarks and gluons. Comparison to experimental data from the Beam Energy Scan II at the Relativistic Heavy Ion Collider or in heavy ion experiments at other accelerators may allow the critical exponents and amplitudes in the scaling equation of state to be determined for QCD if a critical point exists.

The KEK Isotope Separation System (KISS) was used to produce neutron-rich platinum group isotopes via multinucleon transfer reactions. Mass-spectrometry-assisted in-gas-cell laser resonance ionization spectroscopy was utilized to perform the first experimental determinations of the magnetic dipole moment $\mu$ and the differential mean-square charge radii $\delta {\langle r^2\rangle }^{198,A}$ of ${}^{200,201}\mathrm{Pt}$. The quadrupole deformation parameters $|\langle {\beta }_2^2\rangle {|}^{1/2}$ were evaluated from the measured $\delta {\langle r^2\rangle }^{198,A}$ of ${}^{200,201}\mathrm{Pt}$ by using a droplet model. The ${\beta }_2$ values were estimated from a comparison of the experimentally determined magnetic dipole moment $\mu$ with values calculated in a strong coupling model. Comparison of the $|\langle {\beta }_2^2\rangle {|}^{1/2}$ and ${\beta }_2$ values determined from the laser spectroscopy data with theoretical calculations indicates the likely spin-parity value for ${}^{201}\mathrm{Pt}$ to be $I^{\pi }=1/2^{-}$ or $5/2^{-}$.

Fission barriers for supposed doubly magic ${}^{298}\mathrm{Fl}$ are calculated using a specialized binary macroscopic-microscopic method. The microscopic effects are obtained from the developed binary Strutinsky shell correction method. The main input data are the proton and neutron energy levels calculated with the deformed two-center shell model. One is able in this way to provide the microscopic transition via the level schemes, from the parent to two overlapped and finally separated level schemes. The macroscopic part is acquired by the deformed charged liquid drop model with the double Yukawa-plus-exponential finite range potential. The method is applied to the reactions accompanied by isotopes of Sn and Pb within the fission channels, as being favored by strongly negative shell corrections.

Reduced-basis methods provide a powerful framework for building efficient and accurate emulators. Although widely applied in many fields to simplify complex models, reduced-basis methods have only been recently introduced into nuclear physics. In this Letter we build an emulator to study the single-particle structure of atomic nuclei. By scaling a suitable mean-field Hamiltonian, a “universal” reduced basis is constructed capable of accurately and efficiently reproduce the entire single-particle spectrum of a variety of nuclei. Indeed, the reduced-basis model reproduces both ground- and excited-state energies as well as the associated wave functions with remarkable accuracy. Our results bode well for more demanding applications that use Bayesian optimization to calibrate nuclear energy density functionals.

The variational quantum eigensolver (VQE) is an algorithm to compute ground and excited state energy of quantum many-body systems. A key component of the algorithm and an active research area is the construction of a parametrized trial wave function—a so-called variational ansatz. The wave function parametrization should be expressive enough, i.e., represent the true eigenstate of a quantum system for some choice of parameter values. On the other hand, it should be trainable, i.e., the number of parameters should not grow exponentially with the size of the system. Here, we apply VQE to the problem of finding ground and excited state energies of the odd-odd nucleus ${}^6\mathrm{Li}$. We study the effects of ordering fermionic excitation operators in the unitary coupled clusters ansatz on the VQE algorithm convergence by using only operators preserving the $J_z$ quantum number. The accuracy is improved by two orders of magnitude in the case of descending order. We first compute optimal ansatz parameter values using a classical state-vector simulator with arbitrary measurement accuracy and then use those values to evaluate energy eigenstates of ${}^6\mathrm{Li}$ on a superconducting quantum chip from IBM. We post-process the results by using error mitigation techniques and are able to reproduce the exact energy with an error of $3.8\%$ and $0.1\%$ for the ground state and for the first excited state of ${}^6\mathrm{Li}$, respectively.

$\alpha$ cluster structure in nuclei has been long understood based on the geometrical configuration picture. By using the spatially localized Brink $\alpha$ cluster model in the generator coordinate method, it is shown that the $\alpha$ cluster structure has the apparently opposing duality of crystallinity and condensation, a property of supersolids. To study the condensation aspects of the $\alpha$ cluster structure a field theoretical superfluid cluster model (SCM) is introduced, in which the order parameter of condensation is incorporated by treating rigorously the Nambu-Goldstone mode due to spontaneous symmetry breaking of the global phase. The $\alpha$ cluster structure of ${}^{40}\mathrm{Ca}$, which has been understood in the crystallinity picture, is studied by the SCM with ten $\alpha$ clusters. It is found that the $\alpha$ cluster structure of ${}^{40}\mathrm{Ca}$ is reproduced by the SCM in addition to ${}^{12}\mathrm{C}$ reported in a previous paper, which gives support to the duality of the $\alpha$ cluster structure. The emergence of the mysterious $0^{+}$ state at the lowest excitation energy near the $\alpha$ threshold energy is understood to be a manifestation of the Nambu-Goldstone zero mode, a soft mode, due to the condensation aspect of the duality similar to the Hoyle state in ${}^{12}\mathrm{C}$. The duality of $\alpha$ cluster structure with incompatible crystallinity and coherent wave nature due to condensation is the consequence of the Pauli principle, which causes clustering.

The possible stable and radioactive beam-induced hot fusion reactions for the production of new superheavy element (SHE) $Z=120$ are investigated within the dinuclear system model. Our investigation shows that the reaction ${}^{45}\mathrm{Sc}+{}^{252}\mathrm{Es}$ has a relatively large evaporation residue cross-section (ERCS) for the synthesis of SHE $Z=120$ due to its slightly larger mass asymmetry. In addition, we analyzed the effects of fission barrier and neutron separation energy of superheavy nuclei on ERCS. To synthesize the double-magic $Z=120$ and $N=184$ nucleus predicted by the relativistic mean-field model, some radioactive beam-induced fusion reactions, which can be performed in available experimental equipment, for producing superheavy nucleus ${}^{304}120$ in neutron evaporation channels are investigated systematically. We find that the hot fusion reaction ${}^{50}\mathrm{Ca}+{}^{257}\mathrm{Fm}$ in the $3n$ evaporation channel is optimal for synthesizing the superheavy nucleus ${}^{304}120$. We hope these predictions will shed new light timely for the recent experiments on the synthesis of $Z=120$ superheavy element and the search for superheavy stability islands.

Measurements of inclusive single-proton removal cross sections from a variety of oxygen isotopes incident at intermediate energies are collected to be compared with Glauber reaction model predictions using shell-model spectroscopic factors between the initial projectile ground state and configurations of the bound core state$+$valence proton orbit. The collection of data includes a long oxygen isotopic chain spanning over ${}^{13–20}\mathrm{O}$ and ${}^{22}\mathrm{O}$ with relatively high beam energies of $305–635\mathrm{MeV}$/nucleon, which facilitates a probe into the reaction-model origin of the dependence of the spectroscopic strength reduction factor $R_{\mathrm{s}}$ (the ratio of the experimental over theoretical single-nucleon removal cross sections) on the binding depth $\mathrm{\Delta }S$ of the removed nucleon, as high beam energies enhance the applicability of the eikonal and sudden approximation that underlie the Glauber model. Our analysis gives $R_{\mathrm{s}}$ values that largely conform to the former $R_{\mathrm{s}}\text{−}\mathrm{\Delta }S$ systematics established upon data mainly over beam energies of $80–240\mathrm{MeV}/\mathrm{nucleon}$, yet with a slightly dampened $R_s\text{−}\mathrm{\Delta }S$ dependence, and also signs of an odd-even staggering of $R_s$ with respect to the projectile mass number $A$.

The fusion mechanics of ${}^{58}\mathrm{Ni}+{}^{64}\mathrm{Ni}$ and ${}^{64}\mathrm{Ni} +{}^{64}\mathrm{Ni}$ reactions is analyzed by using the energy dependent Woods-Saxon potential (EDWSP) model and the subsequent decay dynamics of ${}^{122}\mathrm{Ba}^{*}$ and ${}^{128}\mathrm{Ba}^{*}$ isotopes formed in these fusion channels is examined via the dynamical cluster-decay model (DCM). In the EDWSP model, the energy dependent nature of the Woods-Saxon potential causes modifications in the profile of the fusion barrier between fusing nuclei. Such barrier modifications lead to the lowering of the effective fusion barrier of the colliding nuclei. Hence, EDWSP outcomes satisfactorily describe the energy dependence of fusion cross sections of the chosen reactions in near- and sub-barrier energy regions. Following this, the fragmentation of compound nuclei ${}^{122}\mathrm{Ba}^{*}$ and ${}^{128}\mathrm{Ba}^{*}$ formed using the above-mentioned reactions is investigated by using the collective clusterization approach of DCM. The calculations are done for quadrupole $\left({\beta }_2\right)$ choice of fragmentation with hot configurations having optimized orientations. The evaporation residues' cross-section data lying within beam energy $\left(E_{\mathrm{beam}}\right)$ = 171–220 MeV are nicely addressed. The comparative analysis of decaying ${}^{122}\mathrm{Ba}^{*}$ and ${}^{128}\mathrm{Ba}^{*}$ nuclei is worked out in terms of fragmentation potential and preformation probability, along with the investigation of barrier characteristics.

Based on the preliminary work done in a previous paper [Phys. Rev. C 105, 054001 (2022)], we investigate the effects of laser-induced fusion rate enhancements of different fusion fuels. In the aforementioned work, which considered ${}_1{}^2\mathrm{H}\text{−}{}_1{}^3\mathrm{H}$ (D-T) and ${\mathrm{DHe}}^3$ fusion, it was observed that a larger product of charge numbers of the fusion reactants leads to an increased laser-induced enhancement to the fusion cross section for static external electric fields. We investigate whether this trend persists for DT, ${\mathrm{DHe}}^3$, and ${p\mathrm{B}}^{11}$ fusion for dynamical electric fields, using the semiclassical approaches of the Wentzel-Kramers-Brillouin method and the imaginary-time method, as well as the Kramers-Henneberger method, and the Volkoff-state approximation. We find that the fusion cross section of ${p\mathrm{B}}^{11}$ indeed exhibits the largest relative enhancement for all laser parameters considered and may even surpass the cross section of DT and ${\mathrm{DHe}}^3$ fusion.

The isotopic systematics of Sn isotopes in the range $A=116$–124 were investigated by combining the nuclear structure and reaction calculations for the analysis of ${}^A\mathrm{Sn}(p,p)$ reactions at 295 MeV. The ${}^A\mathrm{Sn}(p,p)$ reactions were calculated employing the relativistic impulse approximation (RIA) with theoretical densities obtained for the Sn isotopes from relativistic Hartree-Bogoliubov (RHB) calculations with the DD-ME2 interaction and nonrelativistic Skyrme Hartree-Fock-Bogoliubov (SHFB) calculations with the SKM* interaction. Calculation using the DD-ME2 density reproduced the experimental data for ${}^{122}\mathrm{Sn}(p,p)$ but overestimated the ${}^{116}\mathrm{Sn}(p,p)$ and ${}^{118}\mathrm{Sn}(p,p)$ cross sections at backward angles. In the isotopic analysis of the cross section ratio $R\left(\sigma \right)$ of ${}^{122}\mathrm{Sn}$ to ${}^{116}\mathrm{Sn}$, a calculation using the SKM* density reproduced the peak amplitudes of $R\left(\sigma \right)$ obtained from the experimental cross sections, whereas a calculation using the DD-ME2 density did not. The ratio $R\left(\sigma \right)$ was found to be sensitive to the isotopic change of the neutron $3s_{1/2}$ occupation through the isotopic difference of the surface neutron density around $r=4$–5 fm. Isotopic analysis indicated that a rapid increase of the $3s_{1/2}$ occupation from ${}^{116}\mathrm{Sn}$ to ${}^{122}\mathrm{Sn}$ obtained by the DD-ME2 calculation is unlikely. This result derived from the 295 MeV ${}^A\mathrm{Sn}(p,p)$ cross section data [S. Terashima et al., Phys. Rev. C 77, 024317 (2008).] is consistent with the direct measurement of the neutron occupations in Sn isotopes by neutron transfer and pickup reactions [S. V. Szwec et al., Phys. Rev. C 104, 054308 (2021).

Nuclear level densities (NLDs) and $\gamma$-ray strength functions (GSFs) of ${}^{120,124}\mathrm{Sn}$ have been extracted with the Oslo method from proton-$\gamma$ coincidences in the ($p,p^{\prime }\gamma )$ reaction. The functional forms of the GSFs and NLDs have been further constrained with the Shape method by studying primary $\gamma$-transitions to the ground and first excited states. The NLDs demonstrate good agreement with the NLDs of ${}^{116,118,122}\mathrm{Sn}$ isotopes measured previously. Moreover, the extracted partial NLD of $1^{-}$ levels in ${}^{124}\mathrm{Sn}$ is shown to be in fair agreement with those deduced from spectra of relativistic Coulomb excitation in forward-angle inelastic proton scattering. The experimental NLDs have been applied to estimate the magnitude of the Porter-Thomas (PT) fluctuations. Within the PT fluctuations, we conclude that the GSFs for both isotopes can be considered to be independent of initial and final excitation energies, in accordance with the generalized Brink-Axel hypothesis. Particularly large fluctuations observed in the Shape-method GSFs present a considerable contribution to the uncertainty of the method and may be one of the reasons for deviations from the Oslo-method strength at low $\gamma$-ray energies and low values of the NLD (below $\approx 1\times {10}^3\text{–}2\times {10}^3{\mathrm{MeV}}^{-1}$).

The nature of the yrast negative-parity band and its chiral-like partner band in ${}^{104}\mathrm{Ag}$ is investigated experimentally and theoretically. Lifetimes of states in the negative-parity yrast band and positive-parity band based on the 4424-keV level are measured using Doppler shift attenuation technique. Lifetimes of three more states have been determined along with the upper limit for the lifetime of the highest observed yrast states. Further, lifetimes known from earlier studies are determined with better precision. The level scheme of ${}^{104}\mathrm{Ag}$ has also been extended with the addition of new enhanced $E1$ transitions linking the positive-parity band based on the 4424-keV levels and the yrast negative-parity and its partner band. $B\left(E1\right)$ and/or $B\left(E1\right)/B\left(M1\right)$ values for the transitions from the positive-parity band to the yrast and its partner band have been determined for the first time; these suggest strong octupole correlation between the positive-parity and the negative-parity bands. Calculations based on the triaxial projected shell model (TPSM) and covariant density functional theory (CDFT) have been performed to unravel the intrinsic structures of the partner band and the excited positive-parity band. TPSM calculations predict that doublet bands have significant angular momentum contributions along the three principle axes, suggesting that bands could have chiral symmetry breaking origin. The CDFT calculations predict a $\pi {\left(g_{9/2}\right)}^{-1}\otimes \nu \left(h_{11/2}\right){(g_{7/2},d_{5/2})}^2$ aligned quasiparticle configuration for the negative-parity doublet bands with deformation parameters $\beta \approx 0.20$ and $\gamma \approx 5^{\circ }$. The partner band could be interpreted as a chiral vibration mode built on top of the yrast band. The excited positive-parity band is predicted to have aligned four quasiparticle configurations, namely, $\pi {\left(g_{9/2}\right)}^{-1}\otimes \nu {\left(h_{11/2}\right)}^2{(g_{7/2},d_{5/2})}^1$. Further, these calculations predict significant octupole softness in ${}^{104}\mathrm{Ag}$ which could be the reason for enhanced $E1$ transitions between the four quasiparticle positive-parity bands and the doublet negative-parity bands.

Scattering of loosely bound light heavy ions in a strong laser field with wavelength in the optical domain is discussed. Within the framework of the Kroll-Watson theory the differential cross section for an arbitrarily polarized monochromatic laser field is derived and its dependence on the number of exchanged photons, intensity, polarization, and scattering geometry is discussed. As study cases one considers the elastic scattering data of some light systems involving loosely bound and neutron rich nuclei that display strong refractive effects in the elastic scattering data at intermediate angles: ${}^6\mathrm{Li}$ on ${}^7\mathrm{Li}$ at laboratory energy $E=20$ MeV and ${}^6\mathrm{Li}$ on ${}^{13}\mathrm{C}$ ($E=38$ MeV). The role of the incoming polarized monochromatic laser field on these reactions is explored using the decomposition of the scattering amplitude in far and near side components.

For electric quadrupole ($E2$) observables, which depend on the large-distance tails of the nuclear wave function, ab initio no-core configuration interaction calculations converge slowly, making meaningful predictions challenging to obtain. Nonetheless, the calculated values for different $E2$ matrix elements, particularly those involving levels with closely related structure (e.g., within the same rotational band) are found to be robustly proportional. This observation suggests that a known value for one observable may be used to determine the overall scale of $E2$ strengths, and thereby provide predictions for others. In particular, we demonstrate that meaningful predictions for $E2$ transitions may be obtained by calibration to the ground-state quadrupole moment. We test this approach for well-measured low-lying $E2$ transitions in ${}^7\mathrm{Li}$ and ${}^9\mathrm{Be}$, then provide predictions for transitions in ${}^8\mathrm{Li}$ and ${}^9\mathrm{Li}$. In particular, we address the $2^{+}\to 1^{+}$ transition in ${}^8\mathrm{Li}$, for which the reported measured strength exceeds ab initio Green's function Monte Carlo predictions by over an order of magnitude.

The unstable nucleus ${}^8\mathrm{Be}$, with its two $\alpha$-cluster configuration, is the doorway to the formation of heavier $\alpha$-cluster nuclei. Most importantly, its the precursor of the production of ${}^{12}\mathrm{C}$ through the Hoyle state, a resonance state of three $\alpha$ clusters, in the helium burning phase of a massive star. The nucleus exhibits a ground state band of rotational states established through $\alpha \text{−}\alpha$ scattering experiments. A subsequent precision particle-$\gamma$ coincidence measurement of the electromagnetic transition between the $4^{+}\to 2^{+}$ excited states also corroborated the evidence for a highly deformed dumb-bell shaped structure of ${}^8\mathrm{Be}$. A simultaneous phenomenological $R$-matrix analysis of the measured capture reaction cross sections along with the elastic excitation function and phase shift data has been performed. The resulting reduced transition strength of $21.96\pm 3.86e^2{\mathrm{fm}}^4$ compares well with the estimated experimental value of $21.0\pm 2.3e^2{\mathrm{fm}}^4$. The $R$-matrix yield of the $B(E2$) value is closer to the prediction of cluster model but about $19\%$ less than the ab initio result.

Short-lived systems such as superheavy nuclei decay mainly by $\alpha$ emission. However, fission fragment emission is also probable, as theoretical calculations prove it. ${}^{298}\mathrm{Fl}$ dynamics decay is studied with a specialized binary macroscopic-microscopic method combined with the mass inertia tensor. The multidimensional WKB tunneling method is used to obtain the penetrabilities and half-lives. The calculations are applied to fission channels around the isotopes of two presumably favored fragments, Pb and Sn. The choice is due to their proton magicity shell correction favorable fission valleys.