The ${}^{119–126}$Sn nuclei have been produced as fission fragments in two reactions induced by heavy ions: ${}^{12}\text{C}+{}^{238}\text{U}$ at a bombarding energy of 90 MeV and ${}^{18}\text{O}+{}^{208}\text{Pb}$ at 85 MeV. Their level schemes have been built from $\gamma$ rays detected using the Euroball array. High-spin states located above the long-lived isomeric states of the even- and odd-$A$ ${}^{120–126}$Sn nuclei have been identified. Moreover, isomeric states lying around 4.5 MeV have been established in ${}^{120,122,124,126}$Sn from the delayed coincidences between the fission fragment detector SAPhIR and the Euroball array. The states located above 3 MeV excitation energy are ascribed to several broken pairs of neutrons occupying the $\nu h_{11/2}$ orbit. The maximum value of angular momentum available in such a high-$j$ shell, i.e., for midoccupation and the breaking of the three neutron pairs, has been identified. This process is observed for the first time in spherical nuclei.

The formalism of linear response theory for Skyrme forces including tensor terms presented by Davesne et al. [Phys. Rev. C 80, 024314 (2009)] is generalized for the case of a Skyrme energy density functional in infinite matter. We also present analytical results for the odd-power sum rules, with particular attention to the inverse energy weighted sum rule, $M_{-1}$, as a tool to detect instabilities in Skyrme functionals.

Fusion reactions ${}^6\mathrm{Li}(d,\alpha ){}^4\mathrm{He}$ and ${}^2\mathrm{H}{(d,p)}^3\mathrm{H}$ were measured in liquid Li. An ultrasonic target system was developed to form acoustic cavitation bubbles in liquid Li as an additional target. The material uncertainties of the target surface, which have been noted in solid target experiments, were completely rejected because contaminants could be removed in the liquid phase. The $\mathrm{Li}+d$ reaction was not affected by the cavitation process, and the derived screening potential was $U_s=543\pm 38$(sta.) ${}_{-153}^{+83}$(sys.) eV. This value can be explained by ionic Debye screening if liquid Li is regarded as a low-temperature dense plasma. The $d+d$ reaction was found to be enhanced several times by Li cavitation, whereas the yield of the $\mathrm{Li}+d$ reaction remained constant; the ultrasonic effect depends strongly on the target conditions. The enhancement is caused not by Coulomb screening but by the high deuteron temperature in the cavity. The temperature was deduced from the energy dependence of the nuclear reaction enhancement rate as $k{T}_d=590\pm 54$(sta.) ${}_{-457}^{+676}$(sys.) eV. A kinematic analysis also yielded consistent results. Although no meaningful bubble fusion events were observed, extremely large reaction enhancements were occasionally observed.

In stellar core-collapse events matter is heated and compressed to densities above nuclear matter saturation density. For progenitor stars with masses above roughly 25$M_{\odot }$, which eventually form black holes, the temperatures and densities reached during the collapse are so high that a traditional description in terms of electrons, nuclei, and nucleons is no longer adequate. We present here an improved equation of state containing, in addition, pions and hyperons. They become abundant in the high-temperature-and-density regime. We study the different constraints on such an equation of state, coming from both hyperonic data and observations of neutron-star properties. To test the zero-temperature versions of our new equations of state, we perform numerical simulations of the collapse of a neutron star to a black hole. We discuss the influence of the additional particles on the thermodynamic properties within the hot versions of the equation of state and we show that, in regimes relevant to core-collapse and black-hole formation, the effects of pions and hyperons on pressure, internal energy, and sound speed are not negligible.

The nucleation process of quark matter in cold ($T=0$) stellar matter is investigated using the microscopic Brueckner-Hartree-Fock approach to describe the hadronic phase and using the MIT bag model, the Nambu–Jona-Lasinio, and the chromodielectric models to describe the deconfined phase of quark matter. The consequences of the nucleation process for neutron star physics are outlined. Hyperonic stars are metastable only for some of the quark matter equations of state considered. The effect of a hyperonic three-body force on the metastability of compact stars is estimated, and it is shown that, except for the Nambu–Jona-Lasinio model and the MIT bag model with a large bag pressure, the other models predict the formation of hybrid stars with a maximum mass not larger than $\sim$1.62$M_{\odot }$.

The symmetry energy in nuclei is studied using a monopole-monopole two-body interaction, which has an isospin-dependent term. A Hartree theory is developed for this interaction which has an oscillator shell-model basis with a corresponding shell structure. The role of shell structure on the symmetry energy is then studied. We also find that the strength of the Heisenberg interaction is very important for understanding the difference between proton and neutron radii and features associated with halo nuclei.

The two-proton removal reaction from ${}^{28}$Mg projectiles has been studied at 93 MeV/u. First coincidence measurements of the heavy ${}^{26}$Ne projectile residues, the removed protons, and other light charged particles enabled the relative cross sections from each of the three possible elastic and inelastic proton removal mechanisms to be determined. These more final-state-exclusive measurements are key for further interrogation of these reaction mechanisms and use of the reaction channel for quantitative spectroscopy of very neutron-rich nuclei. The relative and absolute yields of the three contributing mechanisms are compared to reaction model expectations based on the use of eikonal dynamics and $sd$-shell-model structure amplitudes.

Simple wave functions for ${}^{11,12}$Be have been around for a long time. They have been tested against many independent processes involving (and properties of) these nuclei. All are consistent, except ${}^{11}$Be($d$,$p$), where the discrepancy is a 4.7σ effect for the 2${}^{+}$ state and 15σ for the ground state. Here, we propose a resolution to this dilemma.

We introduce isospin dependence in the cluster recognition algorithms used in the quantum molecular dynamics model to describe fragment formation in heavy ion collisions. This change reduces the yields of emitted nucleons and enhances the yields of fragments, especially heavier fragments. The enhancement of neutron-rich lighter fragments mainly occurs at midrapidity. Consequently, isospin-dependent observables, such as isotope distributions, yield ratios of $n/p$, $t{/}^3\text{He}$, and isoscaling parameters are affected. We also investigate how equilibration in heavy ion collisions is affected by this change.

The quantum description of a particle moving in a deformed potential is investigated. A pseudostate (PS) basis is used to represent the states of the composite system. This PS basis is obtained by diagonalizing the system Hamiltonian in a family of square integrable functions. In this work the transformed harmonic oscillator (THO) functions, obtained from the solutions of the harmonic oscillator using a local scale transformation (LST), are used. The proposed method is applied to the ${}^{11}$Be nucleus, treated in a two-body model (${}^{10}\mathrm{Be}+n$). Structure observables have been studied. Wave functions and energies obtained for the bound states and some low-lying resonances are compared with those obtained by direct integration of the Schrödinger equation. The dipole and quadrupole electric transition probabilities for the low-energy continuum have been calculated in the THO basis, and compared with the exact distributions obtained with the scattering states.

The surrogate nuclear reaction method is being applied in many efforts to indirectly determine neutron-induced reaction cross sections on short-lived isotopes. This technique aims to extract accurate ($n$,$\gamma$) cross sections from measured decay properties of the compound nucleus of interest (created using a different reaction). The advantages and limitations of a method that identifies the $\gamma$-ray decay channel by detecting any high-energy (“statistical”) $\gamma$ ray emitted during the relaxation of the compound nucleus were investigated. Data collected using the Silicon Telescope Array for Reaction Studies and Livermore-Berkeley Array for Collaborative Experiments silicon and germanium detector arrays were used to study the decay of excited gadolinium nuclei following inelastic proton scattering. In many cases, this method of identifying the $\gamma$-ray decay channel can simplify the experimental data collection and greatly improve the detection efficiency for $\gamma$-ray cascades. The results show sensitivity to angular-momentum differences between the surrogate reaction and the desired ($n$,$\gamma$) reaction similar to an analysis performed using low-lying discrete transitions even when ratios of cross sections are considered.

New results for energies of resonances in ${}^{18}$Na have led us to reexamine the problems of ${}^{18}$Na and ${}^{19}$Mg. We have calculated the effect of the new data on energy and decay width of ${}^{19}$Mg (ground state).

Data for the ${}^{14}$C(${}^6$Li,$d$)${}^{18}$O(6.20) reaction, at 20 MeV, provides an α spectroscopic factor of 0.23 for this 1${}^{-}$ state. Assuming equal spectroscopic factors for mirror states, the computed α width for ${}^{18}$Ne(6.15) is 3.9(1.0) eV.

The neutron-deficient nucleus ${}^{173}$Hg has been studied following fusion-evaporation reactions. The observation of the decay of excited states via $\gamma$ radiation are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighboring neutron-deficient Hg nuclei. In addition to the $\gamma$-ray spectroscopy, the $\alpha$ decay of this nucleus has been measured yielding superior precision to earlier measurements.

We consider a spherical volume of hot and dense hadronic matter (fireball) expanding into a vacuum. It is assumed that initially the fireball matter is in local thermal and chemical equilibrium with vanishing collective velocity. The time evolution of the fireball is studied in parallel within the Giessen Boltzmann-Uehling-Uhlenbeck transport model and an ideal hydrodynamic model. The equation of state of an ideal hadronic gas is used in the hydrodynamic calculation. The same set of hadronic species is used in transport and fluid-dynamical simulations. Initial coordinates and momenta of hadrons in transport simulations have been randomly generated by using the Fermi and Bose distributions for (anti)baryons and mesons. The model results for radial profiles of densities and collective velocities of different hadronic species are compared at different times. We find that two considered models predict essential differences in time evolution of hadron abundances, which are especially pronounced for hyperonic species. This gives an evidence of a strong deviation from chemical equilibrium in expanding hadronic matter.

Background: Type Ia supernovae contribute significantly to the nucleosynthesis of many Fe-group and intermediate-mass elements. However, the robustness of nucleosynthesis obtained via models of this class of explosions has not been studied in depth until now.

Purpose: We explore the sensitivity of the nucleosynthesis resulting from thermonuclear explosions of massive white dwarfs with respect to uncertainties in nuclear reaction rates. We put particular emphasis on indentifying the individual reactions rates that most strongly affect the isotopic products of these supernovae.

Method: We have adopted a standard one-dimensional delayed detonation model of the explosion of a Chandrasekhar-mass white dwarf and have postprocessed the thermodynamic trajectories of every mass shell with a nucleosynthetic code to obtain the chemical composition of the ejected matter. We have considered increases (decreases) by a factor of 10 on the rates of 1196 nuclear reactions (simultaneously with their inverse reactions), repeating the nucleosynthesis calculations after modification of each reaction rate pair. We have computed as well hydrodynamic models for different rates of the fusion reactions of ${}^{12}$C and of ${}^{16}$O. From the calculations we have selected the reactions that have the largest impact on the supernova yields, and we have computed again the nucleosynthesis using two or three alternative prescriptions for their rates, taken from the JINA REACLIB database. For the three reactions with the largest sensitivity we have analyzed as well the temperature ranges where a modification of their rates has the strongest effect on nucleosynthesis.

Results: The nucleosynthesis resulting from the type Ia supernova models is quite robust with respect to variations of nuclear reaction rates, with the exception of the reaction of fusion of two ${}^{12}$C nuclei. The energy of the explosion changes by less than $\sim$$4\%$ when the rates of the reactions ${}^{12}\mathrm{C}+{}^{12}\text{C}$ or ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ are multiplied by a factor of $\times 10$ or $\times 0.1$. The changes in the nucleosynthesis owing to the modification of the rates of these fusion reactions are also quite modest; for instance, no species with a mass fraction larger than 0.02 experiences a variation of its yield larger than a factor of 2. We provide the sensitivity of the yields of the most abundant species with respect to the rates of the most intense reactions with protons, neutrons, and $\alpha$. In general, the yields of Fe-group nuclei are more robust than the yields of intermediate-mass elements. Among the species with yields larger than ${10}^{-8}$$M_{\odot }$, ${}^{35}$S has the largest sensitivity to the nuclear reaction rates. It is remarkable that the reactions involving elements with $Z>22$ have a tiny influence on the supernova nucleosynthesis. Among the charged-particle reactions, the most influential on supernova nucleosynthesis are ${}^{30}\mathrm{Si}+p\rightleftarrows {}^{31}\mathrm{P}+\gamma$, ${}^{20}\mathrm{Ne}+\alpha \rightleftarrows {}^{24}\mathrm{Mg}+\gamma$, and ${}^{24}\mathrm{Mg}+\alpha \rightleftarrows {}^{27}\mathrm{Al}+p$. The temperatures at which a modification of their rate has a larger impact are in the range $2\lesssim T\lesssim 4$ GK.

Conclusions: The explosion model (i.e., the assumed conditions and propagation of the flame) chiefly determines the element production of type Ia supernovae and derived quantities such as their luminosity, while the nuclear reaction rates used in the simulations have a small influence on the kinetic energy and final chemical composition of the ejecta. Our results show that the uncertainty in individual thermonuclear reaction rates cannot account for discrepancies of a factor of 2 between isotopic ratios in type Ia supernovae and those in the solar system, especially within the Fe group.

Lifetimes in the yrast bands of the nuclei ${}^{182,186}$Pt have been measured using the Doppler-shift recoil distance technique. The results in both cases—a sharp increase in $B\left(E2\right)$ values at very low spins—may be interpreted as resulting from a mixing between two bands of different quadrupole deformations.

Background: Differential cross sections for the $(p,n)$ and $(n,p)$ reactions on ${}^{90}$Zr over the interval of $0–50$-MeV excitation energy were used to determine the corresponding Gamow-Teller (GT) strengths, and the resulting quenching factor is $\approx$0.9 with respect to the Ikeda sum rule. In this procedure the contribution of the isovector spin monopole (IVSM) strength was subtracted from the total strength without taking into account the interference between the GT and the IVSM modes.

Purpose: To determine the quantitative effect of the IVSM excitation mode on the $L=0$ strength in charge-exchange reactions on several closed-shell nuclei and the Sn isotopic chain.

Method: The fully consistent relativistic Hartree-Bogoliubov model plus proton-neutron relativistic quasiparticle random-phase approximation ($pn$-RQRPA) are employed in the calculation of transition strength in the ${\beta }^{-}$ and ${\beta }^{+}$ channels.

Results: The inclusion of the higher-order terms, that include the effect of finite momentum transfer, in the transition operator shifts a portion of the strength to the high-energy region above the GT resonance. The total strength is slightly enhanced in nuclei with small neutron-to-proton ratios but remains unchanged with increasing neutron excess.

Conclusions: Terms that include momentum transfer in the transition operator act mostly to shift the strength to high excitation energies but hardly affect the total strength. Based on the strength obtained using the full $L=0$ transition operator in the $pn$-RQRPA calculation, we have estimated the impact of the IVSM on the strength measured in the charge-exchange reactions on ${}^{90}$Zr and found that the data are consistent with the Ikeda sum rule.

The mean values of a many-body Hamiltonian including a proton-neutron pairing term and matrix elements of one-, two-, and four-body operators within a basis of particle-number-projected BCS states are analytically expressed in terms of a single function $Q\left(N\right)$ depending on the number of particles, $N$. The function $Q\left(N\right)$ is calculated using a recursion in $N$ in which the shells and the BCS angles are kept the same for any iteration step. An illustrative example is numerically considered in a restricted single-particle space. Some specific features of the standard BCS, the projection after variation approach, and the variation after projection formalism are pointed out.

The ${}^{92}$Mo($n,\gamma$) cross section was obtained using both the absolute surrogate approach and surrogate ratio method (SRM), relative to the ${}^{94}$Mo($n,\gamma$) cross section, in an equivalent neutron energy range of 80 to 890 keV. Excited ${}^{93}$Mo and ${}^{95}$Mo nuclei were populated using the ${}^{92}$Mo($d,p$) and ${}^{94}$Mo($d,p$) reactions, respectively. Both discrete and statistical tagging approaches were employed to identify the $\gamma$-decay channel and were examined in terms of their sensitivity to the initial angular momentum population distribution. The absolute surrogate ${}^{92}$Mo($n,\gamma$) cross sections disagree with evaluated neutron capture cross section data by as much as a factor of 4, whereas the results obtained using the SRM trend more favorably with the evaluated result. Experimental results suggest that discrete and statistical tagging approaches may sample different contributions of the $\gamma$ cascade for near-spherical nuclei. This work uses the surrogate method in the determination of neutron capture cross sections on spherical and quasispherical nuclei in the mass-90 region and provides a possible pathway to extend the SRM to a broader mass range.