The total bremsstrahlung flux-averaged cross sections $\langle \sigma \left(E_{\gamma \max }\right)\rangle$ for the photonuclear reactions ${}^{181}\mathrm{Ta}{(\gamma ,xn;x\le 8)}^{181-x}\mathrm{Ta}$ have been measured in the range of end-point energies $E_{\gamma \max }$ up to 95 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 with the use of the activation and offline $\gamma$-ray spectrometric technique. The calculation of average cross sections was carried out using the cross section values computed with the talys1.95 code for different level density models $LD$ 1–6. A comparison between the experimental total cross sections $\langle \sigma \left(E_{\gamma \max }\right)\rangle$ and the theoretical values has shown satisfactory agreement for the ${}^{181}\mathrm{Ta}(\gamma ,xn)$ reactions with the escape of 1–7 neutrons.

A concept of isospin blocking in the process of isospin diffusion in heavy-ion collisions is raised. Generally, in the process of isospin diffusion, isospin asymmetry would diffuse from the place with large asymmetry to the place with small asymmetry. However, our study shows that the isospin diffusion could be blocked in cases where the local value of the symmetry energy is larger. We dub this phenomenon “isospin blocking”. To check this behavior, in the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, isospin diffusions in the isotope $\mathrm{Sn}+\mathrm{Sn}$ reactions at 270 MeV/nucleon are studied. It is shown that the value of the after-diffusion asymmetry is distinctly blocked if the local symmetry energy is large. The effects of the isospin blocking on the isospin asymmetry of dilute and dense matter and the final ${\pi }^{-}/{\pi }^{+}$ ratio in heavy ion collisions are demonstrated.

Lifetimes and reduced transition probabilities were determined in the ground-state band in ${}^{104}\mathrm{Pd}$ up to the ${12}^{+}$ state employing the recoil distance Doppler-shift method. Excited states were populated via the fusion-evaporation reaction ${}^{96}\mathrm{Zr}({}^{12}\mathrm{C},4n){}^{104}\mathrm{Pd}$ at 55 MeV. The $B(E2;2_1^{+}\to 0_{\mathrm{g}.\mathrm{s}.}^{+})$ value deviates from previous evaluated values obtained by Coulomb excitation and electron scattering. The transition strengths for higher-lying states were obtained for the first time, closing a gap in the medium-mass Pd isotope chain. Large-scale shell-model calculations were performed employing the SR88MHJM Hamiltonian along the isotope chain ${}^{96-106}\mathrm{Pd}$ for even-even nuclei and for high-spin states up to ${26}^{+}$ in ${}^{104}\mathrm{Pd}$.

A model is presented that simultaneously describes shape coexistence and quadrupole and octupole collective excitations within a theoretical framework based on the nuclear density functional theory and the interacting boson model. An optimal interacting-boson Hamiltonian that incorporates the configuration mixing between normal and intruder states, as well as the octupole degrees of freedom, is identified by means of self-consistent mean-field calculations using a universal energy density functional and a pairing interaction, with constraints on the triaxial quadrupole and the axially symmetric quadrupole and octupole shape degrees of freedom. An illustrative application to the transitional nuclei ${}^{72}\mathrm{Ge}, {}^{74}\mathrm{Se}, {}^{74}\mathrm{Kr}$, and ${}^{76}\mathrm{Kr}$ shows that the inclusion of the intruder states and the configuration mixing significantly lower the energy levels of the excited $0^{+}$ states, and that the predicted low-lying positive-parity states are characterized by the strong admixture of nearly spherical, weakly deformed oblate, and strongly deformed prolate shapes. The low-lying negative-parity states are shown to be dominated by the deformed intruder configurations.

The basic version of the semimicroscopic particle-hole dispersive optical model is adopted and implemented to describe main properties of the Gamow-Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell parent nuclei. Calculation results obtained for ${}^{48}\mathrm{Ca}, {}^{90}\mathrm{Zr}, {}^{132}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ are compared with available experimental data.

The assignment of the first $2^{+}$ state in ${}^{62}\mathrm{Ga}$ has long been debated, due to its implications in triplet energy difference systematics in this mass region. An experiment has been performed at the IFIN-HH 9-MV Tandem accelerator using the ROSPHERE array in a mixed configuration of ${\mathrm{LaBr}}_3$(Ce) and HPGe detectors, as well as an additional array of liquid scintillator neutron detectors. Excited states in ${}^{62}\mathrm{Ga}$ were populated through a $2n$ fusion-evaporation channel and an anisotropy ratio was obtained from neutron-filtered HPGe statistics of transitions observed at different angles. A $2^{+}$ state has been confirmed at an excitation energy of 978.1(1) keV. Theoretically, the interplay between isospin-symmetry breaking and shape-coexistence effects in the $A=62$ isovector triplet is self-consistently treated within the beyond-mean-field complex excited Vampir variational model with symmetry projection before variation using an effective interaction obtained from a G matrix based on the charge-dependent Bonn CD potential adding the Coulomb interaction between the valence protons. Results are presented on Coulomb energy differences, mirror energy differences, triplet energy differences, and the superallowed Fermi $\beta$ decay of the ground state of ${}^{62}\mathrm{Ge}$ and ${}^{62}\mathrm{Ga}$.

To take full advantage of experimental facilities such as the Facility for Rare Isotope Beams (FRIB) for applications to nuclear astrophysics, nuclear structure, and explorations of neutrinos and fundamental symmetries, we need a better understanding of the interplay of reaction and structure theory. The renormalization group (RG) is the natural tool for maintaining a consistent treatment of reaction and structure. Here we make a first study of RG for optical potentials, which are important ingredients for direct reactions. To simplify the analysis, we use a pedagogical one-dimensional model and evolve toward low RG resolution using the similarity RG (or SRG). We show how SRG decoupling at low resolution carries over to the optical potential and enhances perturbative approximations, and how induced SRG nonlocality compares to the nonlocality of the optical potential. We discuss the results in the larger context of consistent SRG evolution of operators and wave functions in the analysis of direct reactions.

The long-standing controversy about the isospin dependence of the effective Dirac mass in ab initio calculations of asymmetric nuclear matter is clarified by solving the relativistic Brueckner-Hartree-Fock equations in the full Dirac space. The symmetry energy and its slope parameter at the saturation density are $E_{\text{sym}}\left({\rho }_0\right)=33.1$ MeV and $L=65.2$ MeV, in agreement with empirical and experimental values. Further applications predict the neutron star radius $R_{1.4M_{\odot }}\approx 12$ km and the maximum mass of a neutron star $M_{\text{max}}\le 2.4M_{\odot }$.

Pion exchange is the central ingredient to nucleon-nucleon interactions used in nuclear structure calculations, and one-pion exchange (OPE) enters at leading order in chiral effective field theory. In the ${}^{2S+1}{L}_J={}^1{S}_0$ partial wave, however, OPE and a contact term needed for proper renormalization fail to produce the qualitative, and quantitative, features of the scattering phase shifts. Cutoff variation also revealed a surprisingly low breakdown momentum ${\mathrm{\Lambda }}_{\text{b}}\approx 330$ MeV in this partial wave. Here we show that potentials consisting of OPE, two-pion exchange (TPE), and a single contact address these problems and yield accurate and renormalization group (RG) invariant phase shifts in the ${}^{1}S_0$ partial wave. We demonstrate that a leading-order potential with TPE can be systematically improved by adding a contact quadratic in momenta. For momentum cutoffs $\mathrm{\Lambda }\lesssim 500$ MeV, the removal of relevant physics from TPE loops needs to be compensated by additional contacts to keep RG invariance. Inclusion of the $\mathrm{\Delta }$ isobar degree of freedom in the potential does not change the strong contributions of TPE.

Level schemes of the proton-rich nuclei, ${}^{47}\mathrm{Mn}$ ($Z=25,N=22$) and ${}^{45}\mathrm{Cr}$ ($Z=24,N=21$), have been established for the first time. The technique of mirrored one- and two-nucleon knockout reactions was applied to the secondary beams of ${}^{48}\mathrm{V}/{}^{48}\mathrm{Mn}$ and ${}^{47}\mathrm{V}/{}^{47}\mathrm{Cr}$ to populate states in ${}^{47}\mathrm{Ti}/{}^{47}\mathrm{Mn}$ and ${}^{45}\mathrm{Sc}/{}^{45}\mathrm{Cr}$, respectively. Mirror energy differences (MED) have been studied between the mirrored $T=\frac{3}{2}$ states for both mirror pairs and interpreted using both a shell-model approach and a density-functional-theory approach using the no-core configuration-interaction method. MED in this mass region provide a stringent test of the model prescriptions since both $\mathit{fp}$- and $\mathit{sd}$-shell orbitals are active and, in ${}^{45}\mathrm{Cr}$, spherical and well-deformed structures coexist near the ground state. The inclusive and exclusive one-nucleon removal cross sections have been determined for the populated states in ${}^{47}\mathrm{Ti}/{}^{47}\mathrm{Mn}$ and compared with results from reaction-model calculations.

Due consideration of proton optical-model potential (OMP) anomalies at sub-Coulomb energies for medium-weight nuclei is shown to be critical for the analysis of the unprecedented measurement of ${}^{59}\mathrm{Cu}(p,\alpha ){}^{56}\mathrm{Ni}$ reaction cross section at an energy of $\approx 6$ MeV [Randhawa et al., Phys. Rev. C 104, L042801 (2021)]. The variation in predicted cross sections from standard statistical-model calculations and the cross-section range corresponding to the anomalous proton imaginary-potential depth, for target nuclei off the line of stability, are distinct and well separated. Consequently, the new measurement provides, under unique conditions, tests of proton isoscalar and isovector real-potential components, the anomalous imaginary potential, as well as previous $\alpha$-particle OMP, for nuclei off the line of stability.

Background: Asymptotic giant branch stars are one of the possible sites of fluorine production as confirmed by astronomical observation. The ${}^{15}\mathrm{N}(n,\gamma ){}^{16}\mathrm{N}$ reaction competes with ${}^{15}\mathrm{N}(\alpha ,\gamma ){}^{19}\mathrm{F}$ on the reaction chain and thus influences the production of the only stable fluorine isotope ${}^{19}\mathrm{F}$. The ${}^{15}\mathrm{N}(n,\gamma ){}^{16}\mathrm{N}$ reaction rate at low temperatures of astrophysical interest depends on the neutron spectroscopic factors of the four low-lying states in ${}^{16}\mathrm{N}$.

Purpose: The ${}^{16}\mathrm{N}$ neutron spectroscopic factors from two previous measurements of $(d,p)$ reaction differ by a factor of $\approx 2$. This work was intended to investigate these spectroscopic factors via a precision measurement of the ${}^{15}\mathrm{N}(d,p){}^{16}\mathrm{N}$ angular distributions using a Q3D magnetic spectrograph.

Methods: The high resolution of the Q3D magnetic spectrograph led to clear separation of these four closely spaced states. The neutron spectroscopic factors were extracted from the present angular distributions with the distorted wave Born approximation and adiabatic distorted wave approximation methods.

Results: The neutron spectroscopic factors of the ${}^{16}\mathrm{N}$ ground, 0.120, 0.298, and 0.397 MeV states were extracted to be $1.32\pm 0.12, 1.33\pm 0.18, 1.10\pm 0.10$, and $1.30\pm 0.14$, respectively. The new results support the conclusion that these four states in ${}^{16}\mathrm{N}$ are all good single-particle levels. The cross section and reaction rate of ${}^{15}\mathrm{N}(n,\gamma ){}^{16}\mathrm{N}$ were calculated based on the present spectroscopic factors.

Conclusions: The present work provides a precision measurement of the spectroscopic factors of the ${}^{16}\mathrm{N}$ states and the resulting ${}^{15}\mathrm{N}(n,\gamma ){}^{16}\mathrm{N}$ reaction rate. The present higher reaction rate of the ${}^{15}\mathrm{N}(n,\gamma ){}^{16}\mathrm{N}$ reaction suggests higher flow through ${}^{15}\mathrm{N}(n,\gamma ){}^{16}\mathrm{N}$ compared with previous expectation.

Lifetimes of yrast states in the rare-earth midshell isotopes ${}^{176,178,180}\mathrm{W}$ have been measured with fast-timing methods using the Cologne iron-free Orange spectrometer and the Cologne HORUS spectrometer and with the recoil distance Doppler shift method using the Cologne coincidence plunger setup. Different fusion evaporation reactions have been used to populated excited states in the investigated nuclei. Lifetimes of the $2_1^{+}$, $4_1^{+}$, $6_1^{+}$, and $8_1^{+}$ yrast states were measured in all three tungsten isotopes and in addition the lifetime of the ${10}_1^{+}$ state was measured in ${}^{176}\mathrm{W}$. Quadrupole deformation parameters, reduced transition probabilities, and ${\text{B}}_{4/2}$ ratios are extracted and discussed in the context of interacting boson model 1 calculations. The results with newly determined signatures largely confirm the investigated tungsten isotopes to be deformed prolate rotors.

Background: The coupled-channels model has been highly successful in interpreting experimental subbarrier fusion. The statistical model framework has traditionally been used to explain the basic features of composite system de-excitation in the above Coulomb barrier region. However, in ${}^{12}\mathrm{C}$-induced reactions with ${}^{182,186}\mathrm{W}$, measured fusion cross sections are significantly lower than those predicted by various theoretical models and by fusion systematics.

Purpose: To investigate the dynamics of heavy ion fusion at energies below and above the Coulomb barrier in the ${}^{12}\mathrm{C}$-induced reactions.

Method: A mass spectrometer was used to study the evaporation residues for the ${}^{12}\mathrm{C}+{}^{182,184,186}\mathrm{W}$ reactions. The measurements ranged from $12\%$ below to $45\%$ above the Coulomb barrier energies. The measured fusion cross sections are compared with coupled channels and statistical model calculations.

Results: The measured fusion cross sections for ${}^{12}\mathrm{C}+{}^{182,184,186}\mathrm{W}$ reactions show reasonably good agreement with coupled-channel calculations. Also, evaporation residue cross sections for ${}^{12}\mathrm{C}+{}^{182,184,186}\mathrm{W}$ reactions in the present experiment along with the fission cross sections from literature are described by statistical model calculations.

Conclusions: We successfully explain the previously reported discrepancy between fusion measurements and calculations based on various theoretical models and by fusion systematics for ${}^{12}\mathrm{C}+{}^{182,186}\mathrm{W}$ reactions.

Starting from a separable pairing force of finite range of nucleons, a new set of the pairing strengths for the ${}^1{S}_0$ hyperon-hyperon pairing based on the quark model is proposed and the ${}^1{S}_0$ hyperon superfluidity in neutron stars with the new hyperon pairing strengths is investigated. The reliable $\mathrm{\Lambda }\mathrm{\Lambda }$ pairing strength is 2/3 times $NN$ pairing strength. The upper limit of $\mathrm{\Sigma }\mathrm{\Sigma }$ pairing strength is 2/3 times $NN$ pairing strength. The lower limit of the ratio of $\mathrm{\Xi }\mathrm{\Xi }$ pairing strength to $NN$ pairing strength is 1. With these pairing strengths, the maximum $\mathrm{\Lambda }\mathrm{\Lambda }$ pairing gap is several tenths of a MeV which can be compared with the results calculated with the widely used pairing force ESC00; because of a low fraction of ${\mathrm{\Sigma }}^{-}$ hyperon, the $\mathrm{\Sigma }$ superfluidity is very weak or even absent in neutron stars; the $\mathrm{\Xi }$ superfluidity is stronger than the results calculated with ESC08c and the ${\mathrm{\Xi }}^{-}{\mathrm{\Xi }}^{-}$ pairing may potentially affect the cooling properties of massive neutron stars.

The statistical distribution and correlation relationship of the empirical neutron-proton ($np$) interaction are analyzed, whereby the interaction strengths are extracted from the binding energies using a known four-point formula. By comparing the correlations of the data and those from numerical simulations of the random number method, it is shown that an additional attractive $np$ interaction persists between the last proton and last neutron in odd-odd nuclei. It provides evidence of the residual $np$ interaction from statistical analysis. The adopted new analytical method might be a useful way to clarify the inherent correlation.

Experiments using a ${}^{48}\mathrm{Ca}$ beam on ${}^{238}\mathrm{U}$ and ${}^{242}\mathrm{Pu}$ targets to produce superheavy nuclei were performed at the gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the SHE Factory at JINR. The decay properties of ${}^{286}\mathrm{Fl}$ and ${}^{287}\mathrm{Fl}$, as well as their α-decay products, were refined after the detection of 25 and 69 new decay chains, respectively. In addition, 16 decay chains of ${}^{283}\mathrm{Cn}$ were observed in the ${}^{238}\mathrm{U}+{}^{48}\mathrm{Ca}$ reaction. The possibility of existing of isomeric states in the ${}^{287}\mathrm{Fl}$ consecutive α decays is discussed. A new α line with an energy of 100–200 keV lower than the main one at 10.19 MeV was observed for the first time for even-even ${}^{286}\mathrm{Fl}$ decay. A maximum cross section of $10.4_{-2.1}^{+3.5}\mathrm{pb}$ was measured for the ${}^{242}\mathrm{Pu}\left({}^{48}\mathrm{Ca},3n\right) {}^{287}\mathrm{Fl}$ reaction.

It is shown that within a truncated partial-wave analysis for photoproduction of two pseudoscalar mesons, it is possible to halve the number of independent partial amplitudes by taking into account parity conservation. In addition, within the framework of the proposed formalism, one can rather easily resolve the double discrete ambiguity arising from the symmetry under complex conjugation of the helicity amplitudes. This leads to essential simplifications of the complete experiment problem, at least, as far as mathematical aspects are concerned.