Background: One of the primary objectives of the field of Nuclear Astrophysics is the study of the elemental and isotopic abundances in the universe. Although significant progress has been made in understanding the mechanisms behind the production of a large number of nuclides in the isotopic chart, there are still many open questions regarding a number of neutron-deficient nuclei, the $p$ nuclei. To that end, experimentally deduced nuclear reaction cross sections can provide invaluable input to astrophysical models.

Purpose: The reactions ${}^{107,109}\mathrm{Ag}$($p,\gamma$)${}^{108,110}\mathrm{Cd}$ have been studied at energies inside the astrophysically relevant energy window in an attempt to provide experimental data required for the testing of reaction-rate predictions in terms of the statistical model of Hauser-Feshbach around the $p$ nucleus ${}^{108}\mathrm{Cd}$.

Methods: The experiments were performed with in-beam $\gamma$-ray spectroscopy with proton beams accelerated by the Tandem Van de Graaff Accelerator at NCSR “Demokritos” impinging a target of natural silver. A set of high-purity germanium detectors was employed to record the emitted radiation.

Results: A first set of total cross-section measurements in radiative proton-capture reactions involving ${}^{107,109}\mathrm{Ag}$, producing the $p$-nucleus ${}^{108}\mathrm{Cd}$, inside the astrophysically relevant energy window is reported. The experimental results are compared to theoretical calculations, using talys. An overall good agreement between the data and the theoretical calculations has been found.

Conclusions: The results reported in this work add new information to the relatively unexplored $p$ process. The present measurements can serve as a reference point in understanding the nuclear parameters in the related astrophysical environments and for future theoretical modeling and experimental works.

Decay of the $8^{+}$ isomer in fully stripped ions ${}^{94}\mathrm{Ru}^{44+}$ is observed during its circulation in the experimental Cooler Storage Ring (CSRe) at the Heavy Ion Research Facility in Lanzhou (HIRFL). The ${}^{94}\mathrm{Ru}^{44+}$ ions were produced via projectile fragmentation and stored in CSRe tuned into the isochronous ion-optical mode. The timing signals of the ions, passing through a time-of-flight detector, were consecutively registered and used to determine the variation of revolution time as a function of revolution number. A sudden change of the revolution time at a specific revolution was identified as a fingerprint of the ${}^{94}\mathrm{Ru}^{44+}$ isomer decay. The isomeric half-life was deduced to be 102(17) $\mu \mathrm{s}$, which agrees well with the theoretical expectation by blocking the internal conversion decay of the isomer. Our work proved the feasibility of studying decays of short-lived isomers in high atomic charge states using the isochronous mass spectrometry. In addition, ${}^{94m}\mathrm{Ru}^{44+}$ represents the shortest-lived nuclear state whose mass has ever been measured directly.

The transfer reaction between two nuclei in the superfluid phase is studied with the time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory. To restore the symmetry of the relative gauge angle, a set of independent TDHFB trajectories is taken into account. Then, the transfer probability is computed using a triple projection method. This method is first tested to determine the transfer probabilities on a toy model and compared to the exact solution. It is then applied to the reactions ${}^{20}\mathrm{O}+{}^{20}\mathrm{O}$ and ${}^{14}\mathrm{O}+{}^{20}\mathrm{O}$ in a realistic framework with a Gogny interaction.

The evaporation residue cross section, the anisotropy of the fission fragments angular distribution, the fission probability, the mass-energy distribution of the fission fragments, and the average prescission neutron multiplicity have been calculated for the compound nucleus ${}^{210}\mathrm{Rn}$ by using four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of the total spin of the compound nucleus to the symmetry axis $K$ were considered in the four-dimensional dynamical model. In the dynamical calculations dissipation coefficient of $K,{\gamma }_k$ was considered as a free parameter, and its magnitude was inferred by fitting measured data on the evaporation residue cross section and the anisotropy of the fission fragments angular distribution for the compound nucleus ${}^{210}\mathrm{Rn}$. It was shown that the results of the calculations are in good agreement with the experimental data by using values of the dissipation coefficient of $K$, equal to ${\gamma }_k=\left(0.185-0.200\right){\left(\mathrm{MeV}\mathrm{zs}\right)}^{-1/\phantom{12}2}$. It also was shown that the influence of the dissipation coefficient of $K$ on the results of the calculations of the fission probability, the mass-energy distribution of the fission fragments, and the average prescission neutron multiplicity for the compound nucleus ${}^{210}\mathrm{Rn}$ is small.

The systems ${}^{32}\mathrm{S}+{}^{40,48}\mathrm{Ca}$ and ${}^{32}\mathrm{S}+{}^{48}\mathrm{Ti}$ at 17.7 MeV/nucleon were investigated with the setup general array for fragment identification and for emitted light particles in dissipative collisions (GARFIELD) plus ring counter (RCo) at Laboratori Nazionali di Legnaro (LNL) of Istituto Nazionale di Fisica Nucleare (INFN). Fusion evaporation (FE), fusion fission (FF), and deep inelastic (DIC) events were identified, also through the comparison with the prediction of a transport model (stochastic mean field, SMF), coupled to GEMINI++ as an afterburner. This work mainly deals with the study of isospin transport phenomena in DIC events. In particular, the isospin diffusion is highlighted by comparing the average isotopic content of the quasiprojectile (QP) remnants observed when the target is the $N=Z$ nucleus ${}^{40}\mathrm{Ca}$ and when it is the neutron-rich ${}^{48}\mathrm{Ca}$. Also, the $d/p$ and $t/p$ ratios for particles forward emitted with respect to the QP were found to increase with increasing $N/Z$ of the target.

The formation of large size clusters and/or their relative motion as possible excitation mode are suggested to be closely related to the origin of deformation in specific cases. In ${}^{32}\mathrm{S}$, the consideration of some excitations in this nucleus as based on the existence of two doubly magic ${}^{16}\mathrm{O}$ clusters offers a possible solution to the long-standing problem of missing quadrupole collectivity in shell-model calculations aiming to describe electromagnetic $E2$ transition strengths and quadrupole moments. To experimentally check again this collectivity, lifetime measurements were performed on ${}^{30}\mathrm{S}$ and ${}^{32}\mathrm{S}$. In ${}^{32}\mathrm{S}$, at least, the reproduction of a number of observables supports the cluster scenario. Additionally, the superdeformed yrast band in ${}^{80}\mathrm{Zr}$ could find an explanation as based on the relative motion of two ${}^{40}\mathrm{Ca}$ clusters. Simultaneously, a necessity arises to revise experimentally some lifetimes derived in the past within the Blaugrund approximation when using the Doppler-shift attenuation method.

Fusion cross sections for the ${}^{11}\mathrm{B}+{}^{197}\mathrm{Au}$ system have been measured at energies around and deep below the Coulomb barrier, to probe the occurrence of fusion hindrance in case of asymmetric systems. A deviation with respect to the standard coupled channels calculations has been observed at the lowest energy. The results have been compared with an adiabatic model calculation that considers a damping of the coupling strength for a gradual transition from sudden to adiabatic regime at very low energies. The data could be explained without inclusion of the damping factor. This implies that the influence of fusion hindrance is not significant within the measured energy range for this system. The present result is consistent with the observed trend between the degree of fusion hindrance and the charge product that reveals a weaker influence of hindrance on fusion involving lighter projectiles on heavy targets.

We study the nature of the low-lying resonance states in mirror nuclei ${}^9\mathrm{Be}$ and ${}^9\mathrm{B}$. Investigations are performed within a three-cluster model. The model makes use of the hyperspherical harmonics, which provides a convenient description of the three-cluster continuum. The dominant three-cluster configurations $\alpha +\alpha +n$ and $\alpha +\alpha +p$ in ${}^9\mathrm{Be}$ and ${}^9\mathrm{B}$, respectively, are taken into account. Dominant decay channels for all resonance states in ${}^9\mathrm{Be}$ and ${}^9\mathrm{B}$ are explored. Much attention is paid to the controversial $1/2^{+}$ resonance states in both nuclei. We study effects of the Coulomb interaction on the energy and width of three-cluster resonances in the mirror nuclei ${}^9\mathrm{Be}$ and ${}^9\mathrm{B}$. We also search for the Hoyle-analog state, which is a key step for alternative ways to synthesize ${}^9\mathrm{Be}$ and ${}^9\mathrm{B}$ in triple collisions of clusters in a stellar environment.

The $\gamma$-rigid solution of the Bohr Hamiltonian with the $\beta$-soft potential and $0^{\circ }\le \gamma \le {30}^{\circ }$ is worked out. The resulting model, called T(4), provides a natural dynamical connection between the X(4) and the Z(4) critical-point symmetries, which thus serves as the critical-point symmetry of the spherical to $\gamma$-rigidly deformed shape phase transition. This point is further justified through comparing the model dynamics with those of the interacting boson model. As a preliminary test, the low-lying structures of ${}^{158}\mathrm{Er}$ are taken to compare the theoretical calculations, and the results indicate that this nucleus could be considered as the candidate of the T(4) model with an intermediate $\gamma$ deformation.

We present the formalism for consistently transforming transition operators within the in-medium similarity renormalization group framework. We implement the operator transformation in both the equations-of-motion and valence-space variants, and present first results for electromagnetic transitions and moments in medium-mass nuclei using consistently evolved operators, including the induced two-body parts. These results are compared to experimental values, and—where possible—the results of no-core shell-model calculations using the same input chiral interaction. We find good agreement between the equations-of-motion and valence-space approaches. Magnetic dipole observables are generally in reasonable agreement with experiment, while the more collective electric quadrupole and octupole observables are significantly underpredicted, often by over an order of magnitude, indicating missing physics at the present level of truncation.

We report the results of a study of rotational bands in ${}^{219}\mathrm{Ra}$ via the ${}^{208}\mathrm{Pb}({}^{14}\mathrm{C},3n)$ reaction to look for evidence that this nucleus is statically octupole deformed. We add 19 $\gamma$ rays not previously observed to the level scheme and extend the two most strongly populated alternating parity bands to $J=51/2$ and 45/2. The magnitude of the energy splitting between the spin-parity doublets in the two bands appears to exclude the possibility that ${}^{219}\mathrm{Ra}$ has a static octupole deformation.

Half-life predictions have been performed for the proton emitters with $Z>50$ in the ground state and isomeric state using the Coulomb and proximity potential model for deformed nuclei (CPPMDN). The agreement of the calculated values with the experimental data made it possible to predict some proton emissions that are not verified experimentally yet. For a comparison, the calculations also are performed using other theoretical models, such as the Gamow-like model of Zdeb et al. [Eur. Phys. J. A 52, 323 (2016)], the semiempirical relation of Hatsukawa et al. [Phys. Rev. C 42, 674 (1990)], and the CPPM of Santhosh et al. [Pramana 58, 611 (2002)]. The Geiger-Nuttall law, originally observed for $\alpha$ decay, studied for proton radioactivity is found to work well provided it is plotted for the isotopes of a given proton emitter nuclide with the same $\ell$ value. The universal curve is found to be valid for proton radioactivity also as we obtained a single straight line for all proton emissions irrespective of the parents. Through the analysis of the experimentally measured half-lives of 44 proton emitters, the study revealed that the present systematic study lends support to a unified description for studying $\alpha$ decay, cluster radioactivity, and proton radioactivity.

Multiparticle azimuthal cumulants, often used to study collective flow in high-energy heavy-ion collisions, have recently been applied in small collision systems such as $pp$ and $p+A$ to extract the second-order azimuthal harmonic flow $v_2$. Recent observation of four-, six-, and eight-particle cumulants with “correct sign” $c_2\left\{4\right\}<0$, $c_2\left\{6\right\}>0$, $c_2\left\{8\right\}<0$ and approximate equality of the inferred single-particle harmonic flow, $v_2\left\{4\right\}\approx v_2\left\{6\right\}\approx v_2\left\{8\right\}$, have been used as strong evidence for a collective emission of all the soft particles produced in the collisions. We show that these relations in principle could be violated due to the non-Gaussianity in the event-by-event fluctuation of flow and/or nonflow. Furthermore, we show, using $pp$ events generated with the pythia model, that $c_2\left\{2k\right\}$ obtained with the standard cumulant method are dominated by nonflow from dijets. An alternative cumulant method based on two or more $\eta$-separated subevents is proposed to suppress the dijet contribution. The new method is shown to be able to recover a flow signal as low as 4% imposed on the pythia events, independently of how the event activity class is defined. Therefore the subevent cumulant method offers a more robust way of studying collectivity based on the existence of long-range azimuthal correlations between multiple distinct $\eta$ ranges. The prospect of using the subevent cumulants to study collective flow in $A+A$ collisions, in particular its longitudinal dynamics, is discussed.

The recent data on $B\left(E2\right)$ values, deduced from the multi-Coulex excitation of the low spin states in the decay of ${}^{152}\mathrm{Sm}$, and other experimental findings in the last two decades are compared with the predictions from the microscopic dynamic pairing plus quadrupole model of Kumar and Baranger. The 1292.8 keV $2^{+}$ state is assigned to the ${0_3}^{+}$ band, and the $K=2$ assignment of the 1769 keV $2^{+}$ state is confirmed. The anomaly of the shape coexistence of the assumed spherical β band versus the deformed ground band is resolved. The values from the critical point symmetry X(5) support the collective character of the β band. The problem with the two-term interacting boson model Hamiltonian in predicting β and γ bands in ${}^{152}\mathrm{Sm}$ leads to interesting consequences. The collective features of the second excited $K^{\pi }={0_3}^{+}$ band are preferred over the “pairing isomer” view. Also the multiphonon nature of the higher lying $K^{\pi }={2_2}^{+}\beta \gamma$ band and $K^{\pi }=4^{+}$ band are illustrated vis-à-vis the new data and the nuclear structure theory.

The photonuclear reaction in the multi-GeV region occurs because of the electromagnetic and hadronic interactions. The latter originates due to the hadronic fluctuation, i.e., vector meson, of the photon. The total cross section of the reaction is shadowed because of the vector meson–nucleus (hadronic) interaction. To estimate it quantitatively, the cross section of the photonuclear reaction was calculated in the low energy region ($\sim 1–3$ GeV) using the simple vector-meson dominance (SVMD) model, i.e., the low-lying vector mesons (${\rho }^0, \omega$, and $\varphi$ mesons) were considered. The nuclear shadowing is reinvestigated using the generalized vector meson (GVMD) model, where the higher $\rho$ meson effective state (${\rho }^{\prime }$ meson) is taken into account along with the low-lying vector mesons. Using the GVMD model, the total cross section of the photonuclear reaction are calculated in the above mentioned energy region. The calculated results are compared with the measured spectra.

A novel method for measuring nuclear reactions in inverse kinematics with stored ion beams was successfully used to extract the nuclear-matter radius of ${}^{58}\mathrm{Ni}$. The experiment was performed at the experimental heavy-ion storage ring at the GSI facility using a stored ${}^{58}\mathrm{Ni}$ beam at energies of 100 and 150 MeV/u and an internal helium gas-jet target. Elastically scattered $\alpha$-recoils at low momentum transfers were measured with an in-ring detector system compatible with ultrahigh vacuum. Experimental angular distributions were fitted using density-dependent optical model potentials within the eikonal approximation. This permitted the extraction of the point-matter root-mean-square radius of ${}^{58}\mathrm{Ni}$ with an average value of 3.70(7) fm. Results from this work are in good agreement with several experiments performed in the past in normal kinematics. This pioneering experiment demonstrates a major breakthrough towards future investigations with far-from-stability stored beams using the present technique.

We investigate the $\varphi$ meson nuclear transparency using some recent theoretical developments on the $\varphi$ in medium self-energy. The inclusion of direct resonant $\varphi N$ scattering and the kaon decay mechanisms leads to a $\varphi$ width much larger than in most previous theoretical approaches. The model has been confronted with photoproduction data from CLAS and LEPS and the recent proton induced $\varphi$ production from COSY finding an overall good agreement. The results support the need of a quite large direct $\varphi N$-scattering contribution to the self-energy.

We systematically investigate the neutron-skin thickness of neutron-rich nuclei within a compressible droplet model, which includes several parameters characterizing the surface tension and the equation of state (EOS) of asymmetric nuclear matter as well as corrections due to the surface diffuseness. Such a systematic analysis helps towards constraining the EOS parameters of asymmetric nuclear matter and the poorly known density dependence of the surface tension; the latter is estimated with help of available experimental data for the neutron and proton density distributions and the nuclear masses. Validity of the present approach is confirmed by calculating realistic density distributions of Ca, Ni, Zr, Sn, Yb, and Pb isotopes within a microscopic Skyrme-Hartree-Fock+BCS method for various sets of the effective nuclear force. Our macroscopic model accompanied by the diffuseness corrections works well in the sense that it well reproduces the evolution of the microscopically deduced neutron-skin thickness with respect to the neutron number for selected sets of the effective nuclear force. We find that the surface tension of the compressible nuclear droplet is a key to bridging a gap between microscopic and macroscopic approaches.

Background: Inner fission barriers of actinide nuclei have been known for a long time to be unstable with respect to the axial symmetry. On the other hand, taking into account the effect of the relevant adiabatic mass parameter reduces or even may wash out this instability. A proper treatment of the dynamics for both axial and triaxial modes is thus crucial to accurately determine the corresponding fission barriers. This entails in particular an accurate description of pairing correlations.

Purpose: We evaluate the potential energies, moments of inertia, and vibrational mass parameters in a two-dimensional relevant deformation space (corresponding to the usual $\beta$ and $\gamma$ quadrupole deformation parameters) for four actinide nuclei (${}^{236}\mathrm{U}, {}^{240}\mathrm{Pu}, {}^{248}\mathrm{Cm}$, and ${}^{252}\mathrm{Cf}$). We assess the relevance of our approach to describe the dynamics for a triaxial mode by computing the low energy spectra (exploring thus mainly the equilibrium deformation region). We evaluate the inner fission barrier heights releasing the axial symmetry constraint.

Method: Calculations within the Hartree-Fock plus BCS approach are performed using the SkM* Skyrme effective interaction in the particle-hole channel and a seniority force in the particle-particle channel. The intensity of this residual interaction has been fixed to allow a good reproduction of some odd-even mass differences in the actinide region. Adiabatic mass parameters for the rotational and vibrational modes are calculated using the Inglis-Belyaev formula supplemented by a global renormalization factor taking into account the so-called Thouless-Valatin corrections. Spectra are obtained through the diagonalization of the corresponding Bohr collective Hamiltonian.

Results: The experimental low energy spectra are qualitatively well reproduced by our calculations for the considered nuclei. Inner fission barrier heights are calculated and compared with available estimates from various experimental data. The reproduction of the data is better for ${}^{236}\mathrm{U}$ and ${}^{240}\mathrm{Pu}$ (up to about 300 keV) than for ${}^{248}\mathrm{Cm}$ and ${}^{252}\mathrm{Cf}$ (up to about one MeV).

Conclusions: While these results are encouraging, they call for, in particular, a better treatment of pairing correlations, especially as far as the particle number conservation is concerned. Besides, these results could provide a basis for the determination of the least action trajectories which would generate better grounds for the evaluation of fission half lives.

The light-particle emission probability from an excited compound nucleus depends explicitly on the time-evolution of the system as the available internal excitation energy and, consequently, the particle decay widths depend on the instantaneous deformation of the nucleus. The Langevin dynamical model for fission is employed to extract this deformation dependence in pre-scission particle multiplicities by following the propagation of fissioning trajectories up to scission. The variation of particle decay widths with nuclear deformation is accounted more precisely in comparison to the existing calculations. The number of neutrons emitted from different configurations of the compound nucleus are calculated for a detailed analysis. The deformation dependence of particle emission widths is found to be relevant for highly fissile systems where the dynamics is primarily governed by the saddle to scission motion. This dynamical effect essentially predicts the nuclear shape evolution through evaporated light particles and, for a heavy compound system, simultaneous measurement of neutron multiplicities for fission and evaporation residue events can reveal its intricate nature.