The intraband electromagnetic transitions in ${}^{210}$Po and ${}^{210}$Pb are well described within the shell model approach. In contrast, similar transitions in ${}^{212}$Po are one order of magnitude smaller than the experimental values, suggesting the existence of an $\alpha$-cluster component in the structure of this nucleus. To probe this assumption we introduced Gaussian-like components in the single-particle orbitals. We thus obtained an enhancement of intraband transitions, as well as a proper description of the absolute $\alpha$-decay width in ${}^{212}$Po. We analyzed the recently measured unnatural parity states $I^{-}$ in ${}^{212}$Po in terms of the collective octupole excitation in ${}^{208}$Pb coupled to positive parity states in ${}^{210}$Pb. They are connected by relatively large dipole transitions to yrast positive natural parity states. We described $E1$ transitions by using the same $\alpha$-cluster component and an effective neutron dipole charge $e_{\nu }=-eZ/A$. $B\left(E2\right)$ values and absolute $\alpha$-decay width in ${}^{212}$Po are simultaneously described within the shell model plus a cluster component depending upon one free strength parameter.

High-spin properties of the nucleus ${}^{171}$Hf were studied through the ${}^{128}$Te(${}^{48}$Ca,5$n$) reaction. Previously known bands have been extended to significantly higher spins and four new bands have been extracted from these data. The results are discussed within the framework of the cranked shell model aided by a comparison with level structures in the neighboring nuclei. The band crossings at rotational frequencies $\sim$500 keV are interpreted as caused by the alignments of $h_{11/2}$ and $h_{9/2}$ proton orbitals. Band ED2 exhibits an alignment pattern similar to that of band ED1 which was reported in a recent paper and proposed to be built on a second potential energy minimum involving the deformation-driving proton $i_{13/2}\otimes h_{9/2}$ configuration. It is likely that band ED2 is also associated with a deformation enhanced with respect to that of the normal deformed structures. Further experimental investigation is needed to ascertain the nature of this band.

The neutron-rich mass region around $A\approx 100$ presents challenges for modeling the astrophysical $r$ process because of rapid shape transitions. We report on mass measurements using the TITAN Penning trap at TRIUMF-ISAC to attain more reliable theoretical predictions of $r$-process nucleosynthesis paths in this region. A new approach using highly charged ($q=15+$) ions has been applied which considerably saves measurement time and preserves accuracy. New mass measurements of neutron-rich ${}^{94,97,98}$Rb and ${}^{94,97–99}$Sr have uncertainties of less than 4 keV and show deviations of up to 11$\sigma$ when compared to previous measurements. An analysis using a parameterized $r$-process model is performed and shows that mass uncertainties for the $A=90$ abundance region are eliminated.

The pairing Hamiltonian constitutes an important approximation in many-body systems; it is exactly soluble and quantum integrable. On the other hand, the continuum single-particle level density (CSPLD) contains information about the continuum energy spectrum. The question of whether one can use the Hamiltonian with constant pairing strength for correlations in the continuum is still unanswered. In this paper we generalize the Richardson exact solution for the pairing Hamiltonian including correlations in the continuum. The resonant and nonresonant continua are included through the CSPLD. The resonant correlations are made explicit by using the Cauchy theorem. Low-lying states with seniority 0 and 2 are calculated for the even carbon isotopes. We conclude that energy levels can indeed be calculated with constant pairing in the continuum using the CSPLD. It is found that the nucleus ${}^{24}$C is unbound. The real and complex energy representations of the continuum is developed and their differences are shown. The trajectory of the pair energies in the continuum for the nucleus ${}^{28}$C is shown.

The NIMROD-ISiS array was used to study the transverse flow of intermediate mass fragments in 35 MeV/nucleon ${}^{70}\mathrm{Zn}+{}^{70}\mathrm{Zn}$, ${}^{64}\mathrm{Zn}+{}^{64}\mathrm{Zn}$, and ${}^{64}\mathrm{Ni}+{}^{64}\mathrm{Ni}$ reactions. The intermediate mass fragment flow was previously shown to be sensitive to the density dependence of the symmetry energy. To explore the model dependence of the results, the antisymmetrized molecular dynamics, constrained molecular dynamics, and stochastic mean-field models were each compared to the experimental results to extract information on the form of the symmetry energy. The results demonstrate that sensitivity of the models to the nuclear equation of state can vary significantly based on the treatment of the nuclear dynamics. Despite the differences in the sensitivity, improved agreement with the experimental data is observed for each model with a stiff density dependence of the symmetry energy.

The double-differential cross sections for the ${}^{116}$Cd$(p,n)$ and ${}^{116}$Sn$(n,p)$ reactions were measured at 300 MeV for studying the nuclear matrix element of the ${}^{116}$Cd $\beta \beta$ decay. A multipole decomposition technique was applied to the spectra to extract the Gamow-Teller (GT) component. The integrated GT strengths up to an excitation energy of 30 MeV in the intermediate nucleus ${}^{116}$In are $40\pm 6$ and $11\pm 1$ in the $(p,n)$ and $(n,p)$ spectra, respectively, including the component from the isovector spin monopole (IVSM). The spectra are compared with those obtained from a theoretical calculation with a quasiparticle random phase approximation, where the contribution from the IVSM component as well as the interference effect between the GT and IVSM components are fully taken into account.

The neutron-rich cobalt isotopes up to $A=67$ have been studied through multinucleon transfer reactions by bombarding a ${}^{238}$U target with a 460-MeV ${}^{70}$Zn beam. Unambiguous identification of prompt $\gamma$ rays belonging to each nucleus has been achieved using coincidence relationships with the ions detected in a high-acceptance magnetic spectrometer. The new data are discussed in terms of the systematics of the cobalt isotopes and interpreted with large-scale shell-model calculations in the $fpgd$ model space. In particular, very different shapes can be described in ${}^{67}$Co, at the edge of the island of inversion at $N=40$, where a low-lying highly deformed band coexists with a spherical structure.

A recently formulated model of highly-anisotropic and strongly dissipative hydrodynamics is used in $3+1$ dimensions to study behavior of matter produced in ultrarelativistic heavy-ion collisions. We search for possible effects of the initial high anisotropy of pressure on the final soft-hadronic observables. We find that, by appropriate adjustment of the initial energy density and/or the initial pseudorapidity distributions, the effects of the initial anisotropy of pressure may be easily compensated, and the final hadronic observables become insensitive to early dynamics. Our results indicate that the early thermalization assumption is not necessary to describe hadronic data, in particular, to reproduce the measured elliptic flow $v_2$. The complete thermalization of matter (local equilibration) may take place only at times of about 1–2 fm/$c$, in agreement with the results of microscopic models.

Using a gauged flavor SU(3)-invariant hadronic Lagrangian, we calculate the cross sections for the strangeness-exchange reactions $YY\leftrightarrow N\Xi$ ($Y=\Lambda ,\Sigma$) in the Born approximation. These cross sections are then used in the relativistic Vlasov-Uehling-Uhlenbeck transport model to study $\Xi$ production in $\mathrm{Ar}+\mathrm{KCl}$ collisions at incident energy of 1.76A GeV and impact parameter $b=3.5$ fm. We find that including the contributions of hyperon-hyperon scattering channels strongly enhances the yield of $\Xi$, leading to the abundance ratio ${\Xi }^{-}/(\Lambda +{\Sigma }^0)=3.38\times {10}^{-3}$, which is essentially consistent with the recently measured value of $(5.6\pm {1.2}_{-1.7}^{+1.8})\times {10}^{-3}$ by the HADES Collaboration at GSI.

We compute the binding energy of symmetric nuclear matter in the Brueckner-Hartree-Fock approach using chiral two-nucleon and three-nucleon forces. We find strong overbinding, which cannot be remedied by the current version of three-body forces.

The charge-exchange spin-dipole (SD) excitations for both $(p,n)$ and $(n,p)$ channels in ${}^{16}$O are investigated in the fully self-consistent random phase approximation based on the covariant density functional theory. The fine structure of SD excitations in the most up-to-date ${}^{16}$O($\vec{p},\vec{n}$)${}^{16}$F experiment is excellently reproduced without any readjustment in the functional. The SD excitations are characterized by the delicate balance between the $\sigma$- and $\omega$-meson fields via the exchange terms. The fine structure of SD excitations for the ${}^{16}$O($n,p$)${}^{16}$N channel is predicted for future experiments.

The half-life of the 2305-keV, $I^{\pi }=4^{(-)}$ intruder state in ${}^{34}$P has been measured as $t_{1/2}=2.0\left(1\right)$ ns using $\gamma$-ray coincidence, fast-timing techniques with the Bucharest HPGe and LaBr${}_3$:Ce detector array. Excited states in ${}^{34}$P were populated using the ${}^{18}$O${(}^{18}\text{O},pn$${)}^{34}$P fusion-evaporation reaction at a beam energy of 36 MeV. Reduced transition probabilities have been calculated for different values of the $M2/E3$ mixing ratio, ${\delta }_{E3/M2}$, and compared with shell-model estimates. For small values of the mixing ratio, the $B\left(M2\right)$ value was found to be consistent with similar transitions associated with the occupation of neutron $f_{7/2}$ configurations in this mass region.

Configuration-constrained potential-energy-surface calculations have been performed to investigate multi-quasiparticle high-$K$ states built on superdeformed minima in ${}^{192,194,196}$Pb and ${}^{198}$Po. The calculations predict that ${}^{196}$Pb and ${}^{198}$Po would be favorable candidates for the observation of low-lying superdeformed two- and four-quasiparticle high-$K$ states. The possible decay paths and lifetimes that could lead to isomers are evaluated in detail for ${}^{196}$Pb. Comparisons between the predictions and previous observations of octupole-vibrational excitations indicate also that bands built on superdeformed high-$K$ intrinsic states may compete with the octupole-vibrational mode in this mass region. The quadrupole moments of both the collective and intrinsic excitations are analyzed.

Proton emission from nuclei via the nuclear photoeffect in the combined electromagnetic fields of a $\gamma$-ray photon and an intense laser wave is studied. An $S$-matrix approach to the process is developed by utilizing methods known from the theory of nonperturbative laser-atom interactions. As a specific example, photo-proton ejection from halo nuclei is considered. We show that, due to the presence of the laser field, rich sideband structures arise in the photo-proton energy spectra. Their dependence on the parameters and relative orientation of the photon fields is discussed.

A complete, rigorous relativistic field-theory formulation of the nucleon-nucleon ($\mathit{NN}$) bremsstrahlung reaction is presented. The resulting amplitude is analytic, Lorentz covariant and unitary as a matter of course and it is gauge invariant; i.e., it satisfies a generalized Ward-Takahashi identity. The novel feature of this approach is the consistent microscopic implementation of local gauge invariance across all interaction mechanisms of the hadronic systems, thus serving as a constraint for all subprocesses. The formalism is quite readily adapted to approximations and thus can be applied even in cases where the microscopic dynamical structure of the underlying interacting hadronic systems is either not known in detail or too complex to be treated in detail. We point out how the interaction currents resulting from the photon being attached to nucleon-nucleon-meson vertices can be treated by phenomenological four-point contact currents that preserve gauge invariance. In an advance application of the present formalism [Nakayama and Haberzettl, Phys. Rev. C 80, 051001(R) (2009)], such interaction currents were found to contribute significantly in explaining experimental data. In addition, we provide a scheme that permits—through an introduction of phenomenological five-point contact currents—the approximate treatment of current contributions resulting from pieces of the $\mathit{NN}$ interaction that cannot be incorporated exactly. In each case, the approximation procedure ensures gauge invariance of the entire bremsstrahlung amplitude. We also discuss the necessary modifications when taking into account baryonic states other than the nucleon $N$; in detail, we consider the $\Delta \left(1232\right)$ resonance by incorporating the couplings of the $\mathit{NN}$ to the $N\Delta$ and $\Delta \Delta$ systems and the $\gamma N\to \Delta$ transitions.

Cross sections for radiative capture of neutrons have been measured by the activation technique for stable isotopes of Ba with mass numbers 130, 132, 134, 136, and 138. From separate irradiations using thermal and epithermal neutrons, independent values for the thermal cross sections and effective resonance integrals have been determined. Improved values for the radioactive decay half-lives of ${}^{131}$Ba${}^g$, ${}^{131}$Ba${}^m$, ${}^{133}$Ba${}^m$, ${}^{135}$Ba${}^m$, and ${}^{139}$Ba were also obtained. Results of a new measurement of the energies and intensities of the γ rays in the decay of ${}^{139}$Ba are reported, along with β feedings and energies for the excited states in the daughter ${}^{139}$La.

Plastic scintillators are widely used in industry, medicine, and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 and 850 keV. Monte Carlo simulations, incorporating light collection efficiency and energy resolution effects, are used to generate neutron scattering spectra which are matched to observed distributions of scintillation signals to parameterize the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semiempirical formulation of Birks and a $kB$ factor of ($0.014\pm 0.002$) g MeV${}^{-1}$ cm${}^{-2}$ has been determined. Below that energy, the measured quenching factor falls more steeply than predicted by the Birks formalism.

The deformed relativistic Hartree-Bogoliubov theory in continuum with the density-dependent meson-nucleon couplings is developed. The formulism is briefly presented with the emphasis on handling the density-dependent couplings, meson fields, and potentials in an axially deformed system with the partial wave method. Taking the neutron-rich nucleus ${}^{38}$Mg as an example, the newly developed code is verified by the spherical relativistic continuum Hartree-Bogoliubov calculations, where only the spherical components of the densities are considered. When the deformation is included self-consistently, it is shown that the spherical components of density-dependent coupling strengths are dominant, while the contributions from low-order deformed components are not negligible.

The photodisintegration cross section of ${}^4$He into a neutron and helion was measured at incident photon energies of 27.0, 27.5, and 28.0 MeV. A high-pressure ${}^4$He-Xe gas scintillator served as target and detector while a pure Xe gas scintillator was used for background measurements. A NaI detector in combination with the standard HI$\gamma$S scintillator paddle system was employed for absolute photon-flux determination. Our data are in good agreement with the theoretical prediction of the Trento group and the recent data of Nilsson et al. [Phys. Rev. C 75, 014007 (2007)] but deviate considerably from the high-precision data of Shima et al. [Phys. Rev. C 72, 044004 (2005)].