A complete kinematics measurement of the two fission fragments was used for the first time to investigate fission dynamics at small and large deformations. Fissioning systems with high excitation energies, compact shapes, and low angular momenta were produced in inverse kinematics by using spallation reactions of lead projectiles. A new generation experimental setup allowed for the first full and unambiguous identification in mass and atomic number of both fission fragments. This measurement permitted us to accurately determine fission cross sections, the charge distribution, and the neutron excess of the fission fragments as a function of the atomic number of the fissioning system. These data are compared with different model calculations to extract information on the value of the dissipation parameter at small and large deformations. The present results do not show any sizable dependence of the nuclear dissipation parameter on temperature or deformation.

Using two-nucleon and three-nucleon interactions derived in the framework of chiral perturbation theory (ChPT) with and without the explicit $\mathrm{\Delta }$ isobar contributions, we calculate the energy per particle of symmetric nuclear matter and pure neutron matter in the framework of the microscopic Brueckner-Hartree-Fock approach. In particular, we present for the first time nuclear matter calculations using the new fully local in coordinate-space two-nucleon interaction at the next-to-next-to-next-to-leading-order (N3LO) of ChPT with $\mathrm{\Delta }$ isobar intermediate states ($\mathrm{N}3\mathrm{LO}\mathrm{\Delta }$) recently developed by Piarulli et al. [arXiv:1606.06335]. We find that using this $\mathrm{N}3\mathrm{LO}\mathrm{\Delta }$ potential, supplemented with a local N2LO three-nucleon interaction with explicit $\mathrm{\Delta }$ isobar degrees of freedom, it is possible to obtain a satisfactory saturation point of symmetric nuclear matter. For this combination of two- and three-nucleon interactions we also calculate the nuclear symmetry energy and we compare our results with the empirical constraints on this quantity obtained using the excitation energies to isobaric analog states in nuclei and using experimental data on the neutron skin thickness of heavy nuclei, finding a very good agreement in all the considered nucleonic density range. In addition, we find that the explicit inclusion of $\mathrm{\Delta }$ isobars diminishes the strength of the three-nucleon interactions needed to get a good saturation point of symmetric nuclear matter. We also compare the results of our calculations with those obtained by other research groups using chiral nuclear interactions with different many-body methods, finding in many cases a very satisfactory agreement.

The deformation-induced splitting of isoscalar giant monopole resonance (ISGMR) is systematically analyzed in a wide range of masses covering medium, rare-earth, actinide, and superheavy axial deformed nuclei. The study is performed within the fully self-consistent quasiparticle random-phase-approximation method based on the Skyrme functional. Two Skyrme forces, one with a large (SV-bas) and one with a small (SkP) nuclear incompressibility, are considered. The calculations confirm earlier results that, because of the deformation-induced $E0-E2$ coupling, the isoscalar $E0$ resonance attains a double-peak structure and significant energy upshift. Our results are compared with available analytic estimations. Unlike earlier studies, we get a smaller energy difference between the lower and upper peaks and thus a stronger $E0-E2$ coupling. This in turn results in more pumping of $E0$ strength into the lower peak and more pronounced splitting of ISGMR. We also discuss widths of the peaks and their negligible correlation with deformation.

We study the zero-temperature BCS gaps for the triplet channel in pure neutron matter using similarity renormalization group (SRG) evolved interactions. We use the dependence of the results on the SRG resolution scale as a tool to analyze medium and many-body corrections. In particular, we study the effects of including the three-body interactions at leading order, which appear at next-to-next-to leading order (N2LO) in the chiral effective field theory (EFT), as well as that of the first-order self-energy corrections on the zero-temperature gap. In addition we also extract the transition temperature as a function of densities and verify the BCS scaling of the zero-temperature gaps to the transition temperature. We observe that the self-energy effects are very crucial in order to reduce the SRG resolution scale dependence of the results, while the three-body effects at the leading order do not change the two-body resolution scale dependence. On the other hand, the results depend strongly on the three-body cutoff, emphasizing the importance of the missing higher-order three-body effects. We also observe that self-energy effects reduce the overall gap as well as shift the gap closure to lower densities.

Multi-quasiparticle high-$K$ states, several of which are isomeric, were observed in ${}^{180}\mathrm{Hf}$ with the Gammasphere array. Lifetimes in the ns-$\mu \mathrm{s}$ range were determined using centroid-shift and decay measurements within a $\mu \mathrm{s}$ coincidence time window. The configurations of high-$K$ states involve two and four quasiparticles, with states up to $K^{\pi }=\left({18}^{-}\right)$ established. High-$K$ excitations are found to be progressively more favored with increasing excitation energy. The $K$ quantum number is quite robust up to the highest spins observed, as evidenced by the large values of the reduced hindrance for isomeric decays. Rotational bands built on three high-$K$ states are identified, and the measured branching ratios in these sequences enable the assignment of underlying configurations. Multi-quasiparticle calculations using the Lipkin-Nogami approach for pairing, with blocking included, reproduce the observed high-$K$ energies quite well.

The inner crust of neutron stars is supposed to be inhomogeneous and composed of dense structures (clusters) that are immersed in a dilute gas of unbound neutrons. Here we consider spherical clusters forming a body-centered cubic (BCC) crystal and cylindrical rods arranged in a hexagonal lattice. We study the relative motion of these dense structures and the neutron gas using superfluid hydrodynamics. Within this approach, which relies on the assumption that Cooper pairs are small compared to the crystalline structures, we find that the entrainment of neutrons by the clusters is very weak since neutrons of the gas can flow through the clusters. Consequently, we obtain a low effective mass of the clusters and a superfluid density that is even higher than the density of unbound neutrons. Consequences for the constraints from glitch observations are discussed.

An equations of motion phonon method is extended to odd nuclei. It generates an orthonormal basis out of an odd particle coupled to $n$-phonon core states ($n=0,1,2,\cdots$), built of Tamm-Dancoff phonons, and formulates the eigenvalue problem in such a multiphonon particle-core space. ${}^{17}\mathrm{O}$ is chosen as testing ground. An intrinsic chiral Hamiltonian is adopted in a large configuration space to perform a calculation using a Hartree-Fock (HF) basis in a space encompassing up to two and, under simplifying assumptions, three phonons. The impact of the different phonon components on spectrum, moments, transitions, and dipole cross section is discussed.

In this paper we investigate the $I^4$ symmetry energy coefficient $[I=(N-Z)/A]$ extracted from a few popular mass models, and their corresponding databases improved, respectively, by the radial basis function (RBF) approach and the RBF with odd-even corrections. Our results show that the linear correlation between our resultant $I^4$ symmetry energy coefficients (denoted by $c_4^{\left(\mathrm{V}\right)}$) and the corresponding root-mean-square deviations from experimental masses of these theoretical databases is very robust. Interestingly, the extrapolated values of $c_4^{\left(\mathrm{V}\right)}$ using the above three versions of databases are consistent with each other.

Within the framework of the Lanzhou quantum molecular-dynamics transport model, the nuclear fragmentation induced by low-energy antiprotons has been investigated thoroughly. A coalescence approach is developed for constructing the primary fragments in phase space. The secondary decay process of the fragments is described by a well-known statistical code. It is found that the localized energy released in antibaryon-baryon annihilation is deposited in a nucleus mainly via pion-nucleon collisions, which leads to the emissions of pre-equilibrium particles, fission, evaporation of nucleons, light fragments, etc. The strangeness exchange reactions dominate the hyperon production. The averaged mass loss increases with the mass number of target nucleus. A bump structure in the domain of intermediate mass for heavy targets appears owing to the contribution of fission fragments.

The nuclear density dependencies of the neutron and $\mathrm{\Sigma }$ and $\mathrm{\Lambda }$ hyperons are important inputs in the determination of the neutron star mass as the appearance of hyperons coming from strong attractions significantly changes the stiffness of the equation of state (EOS) at iso-spin asymmetric dense nuclear matter. In-medium spectral sum rules have been analyzed for the nucleon, $\mathrm{\Sigma }$, and $\mathrm{\Lambda }$ hyperon to investigate their properties up to slightly above the saturation nuclear matter density by using the linear density approximation for the condensates. The construction scheme of the interpolating fields without derivatives has been reviewed and used to construct a general interpolating field for each baryon with parameters specifying the strength of independent interpolating fields. Optimal choices for the interpolating fields were obtained by requiring the sum rules to be stable against variations of the parameters and the result to be consistent with known phenomenology. The optimized result shows that Ioffe's choice is not suitable for the $\mathrm{\Lambda }$ hyperon sum rules. It is found that, for the $\mathrm{\Lambda }$ hyperon interpolating field, the up and down quark combined into the scalar diquark structure $u^{T}C{\gamma }_{5}d$ should be emphasized to ensure stable sum rules. The quasi-$\mathrm{\Sigma }$ and -$\mathrm{\Lambda }$ hyperon energies are always found to be higher than the quasineutron energy in the region $0.5<\rho /{\rho }_0<1.5$ where the linear density approximation in the sum-rule analysis is expected to be reliable.

A closed expression is derived for the pair vibrational correlation energy generated in the random-phase approximation by the isovector pairing force in the case when Kramers and charge-degenerate single-nucleon levels are uniformly distributed in an interval. The expression is used to analyze the spectral density of pair vibrational frequencies relative to that of two-quasinucleon energies. Applications to the analysis of the symmetry energy of the isovector pairing model and to a Strutinskij renormalization of this model are discussed.

The first rotational sequences have been assigned to the odd-odd nucleus ${}^{168}\mathrm{Re}$. Coincidence relationships of these structures with rhenium x rays confirm the isotopic assignment, while arguments based on the $\gamma$-ray multiplicity ($K$-fold) distributions observed with the new bands lead to the mass assignment. Configurations for the two bands were determined through analysis of the rotational alignments of the structures and a comparison of the experimental $B\left(M1\right)/B\left(E2\right)$ ratios with theory. Tentative spin assignments are proposed for the $\pi h_{11/2}\nu i_{13/2}$ band, based on energy level systematics for other known sequences in neighboring odd-odd rhenium nuclei, as well as on systematics seen for the signature inversion feature that is well known in this region. The spin assignment for the $\pi h_{11/2}\nu (h_{9/2}/f_{7/2})$ structure provides additional validation of the proposed spins and configurations for isomers in the ${}^{176}\mathrm{Au} \to {}^{172}\mathrm{Ir}\to {}^{168}\mathrm{Re} \alpha$-decay chain.

A mechanism of photon-induced direct knockout of a nucleon from the nuclear surface without formation of intermediate excited nuclear state is described. The effect plays an important role at least for the $(\gamma ,p)$ reaction on heavy nuclei in the energy region centered at about 30 MeV where the probability of formation of the giant dipole resonance is already small but quasideuteron photoabsorption still does not prevail. A compact model of the surface direct nuclear photoeffect (SDNP) in heavy deformed nuclei that can be used to calculate the differential $d\sigma (E_{\gamma },\vartheta )/d\mathrm{\Omega }$ and total $\sigma \left(E_{\gamma }\right)$ cross sections of the SDNP under adiabatic approximation is formulated. The model is applied to calculation of the $(\gamma ,p)$ reaction cross sections on ${}^{160}\mathrm{Gd}$ and ${}^{184,186}\mathrm{W}$. The importance of the SDNP effect for these nuclei at $E_{\gamma }\sim 30$ MeV is demonstrated.

The quantum-mechanical time evolution of an isolated β-unstable nuclear state in the context of certain models predicts that the square of the amplitude of the initial undecayed state becomes an approximately exponential function of time on a timescale on the order of ${10}^{-22}–{10}^{-21}\mathrm{s}$. It was argued that a measurement process required to distinguish between the parent and the daughter nuclear states in such a short time would destroy the characteristics of the long-lived β-unstable nuclear state, thus fundamentally restricting the observability of β decay on a short timescale. Since the interaction of the nuclear state with the environment is almost inevitable, we have obtained the timescale of initial non-exponential decay for the nuclear β decay from an estimation of quantum decoherence time considering the atom of the decaying nucleus as a quantum detector. It has been found from such considerations that a decoherence timescale of β decay is on the order of ${10}^{-16}–{10}^{-15}\mathrm{s}$ and the decay should remain reversible and non-exponential on this timescale. The possibilities of observing the effect of non-exponential decay in nuclear systems have been discussed.

Astrophysical environments that reach temperatures greater than $\sim 100$ keV can have significant neutrino energy loss via both plasma processes and nuclear weak interactions. We find that nuclear processes likely produce the highest-energy neutrinos. The important weak nuclear interactions include both charged current channels (electron capture and emission and positron capture and emission) and neutral current channels (deexcitation of nuclei via neutrino pair emission). We show that, in order to make a realistic prediction of the nuclear neutrino spectrum, one must take nuclear structure into account; in some cases, the most important transitions may involve excited states, possibly in both parent and daughter nuclei. We find that the standard technique of producing a neutrino energy spectrum by using a single transition with a $Q$ value and matrix element chosen to fit published neutrino production rates and energy losses will not accurately capture important spectral features.

The ${}^{98}\mathrm{Ru}$ nucleus, populated via the ${}^{97}\mathrm{Mo}({}^3\mathrm{He},2n)$ reaction, has been investigated by means of $K$-internal conversion coefficient, $\gamma$-ray angular distribution, $\gamma -\gamma$ coincidence, and $\gamma -\gamma$ angular correlation measurements. The results have led to an improved knowledge of the excitation energy pattern via the identification of new levels and transitions. New information on spin and parities of many levels as well as on mixing ratios of several transitions has been obtained. The presence of large $M1$ components in many transitions definitely excludes the possibility of considering ${}^{98}\mathrm{Ru}$ as a nucleus having a structure very close to the vibrational one and points to the need of an enlarged framework for a successful description.

Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can trigger the rp-process in type I x-ray bursts. In this environment, a competition between ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ and the two-proton capture reaction ${}^{15}\mathrm{O}(2p,\gamma ){}^{17}\mathrm{Ne}$ is expected.

Purpose: Determine the three-body radiative capture reaction rate for ${}^{17}\mathrm{Ne}$ formation including sequential and direct, resonant and nonresonant contributions on an equal footing.

Method: Two different discretization methods have been applied to generate ${}^{17}\mathrm{Ne}$ states in a full three-body model: the analytical transformed harmonic oscillator method and the hyperspherical adiabatic expansion method. The binary $p-{}^{15}\mathrm{O}$ interaction has been adjusted to reproduce the known spectrum of the unbound ${}^{16}\mathrm{F}$ nucleus. The dominant $E1$ contributions to the ${}^{15}\mathrm{O}(2p,\gamma ){}^{17}\mathrm{Ne}$ reaction rate have been calculated from the inverse photodissociation process.

Results: Three-body calculations provide a reliable description of ${}^{17}\mathrm{Ne}$ states. The agreement with the available experimental data on ${}^{17}\mathrm{Ne}$ is discussed. It is shown that the ${}^{15}\mathrm{O}(2p,\gamma ){}^{17}\mathrm{Ne}$ reaction rates computed within the two methods agree in a broad range of temperatures. The present calculations are compared with a previous theoretical estimation of the reaction rate.

Conclusions: It is found that the full three-body model provides a reaction rate several orders of magnitude larger than the only previous estimation. The implications for the rp-process in type I x-ray bursts should be investigated.

A reanalysis of unpolarized electron-proton elastic scattering data is done in terms of the electric to magnetic form factor squared ratio. This observable is in principle more robust against experimental correlations and global normalizations. The present analysis shows indeed that it is a useful quantity that contains reliable and coherent information. The comparison with the ratio extracted from the measurement of the longitudinal to transverse polarization of the recoil proton in polarized electron-proton scattering shows that the results are compatible within the experimental errors. Limits are set on the kinematics where the physical information on the form factors can be safely extracted. The results presented in this work bring a decisive piece of information to the controversy on the deviation of the proton form factors from the dipole dependence.

Background: $\alpha$-nucleus potentials play an essential role for the calculation of $\alpha$-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions and to the energy dependence of the effective $\alpha$-nucleus potentials.

Purpose: The present work studies the total reaction cross section ${\sigma }_{\mathrm{reac}}$ of $\alpha$-induced reactions at low energies which can be determined from the elastic scattering angular distribution or from the sum over the cross sections of all open nonelastic channels.

Method: Elastic and inelastic ${}^{64}\mathrm{Zn}(\alpha ,\alpha ){}^{64}\mathrm{Zn}$ angular distributions were measured at two energies around the Coulomb barrier, at 12.1 and 16.1 MeV. Reaction cross sections of the $(\alpha ,\gamma ), (\alpha ,n)$, and $(\alpha ,p)$ reactions were measured at the same energies using the activation technique. The contributions of missing nonelastic channels were estimated from statistical model calculations.

Results: The total reaction cross sections from elastic scattering and from the sum of the cross sections over all open nonelastic channels agree well within the uncertainties. This finding confirms the consistency of the experimental data. At the higher energy of 16.1 MeV, the predicted significant contribution of compound-inelastic scattering to the total reaction cross section is confirmed experimentally. As a by-product it is found that most recent global $\alpha$-nucleus potentials are able to describe the reaction cross sections for ${}^{64}\mathrm{Zn}$ around the Coulomb barrier.

Conclusions: Total reaction cross sections of $\alpha$-induced reactions can be well determined from elastic scattering angular distributions. The present study proves experimentally that the total cross section from elastic scattering is identical to the sum of nonelastic reaction cross sections. Thus, the statistical model can reliably be used to distribute the total reaction cross section among the different open channels.