Dipole excitations in the semimagic $N=50\mathrm{}$ nucleus ${}^{87}\mathrm{Rb}$ were investigated at the Stuttgart Dynamitron facility using bremsstrahlung with an end-point energy of 4.0 MeV. The widths $\Gamma$ or the reduced excitation probabilities $B\left(\Pi 1\right)\uparrow$ of 18 states were determined for the first time. The magnetic dipole excitations are well reproduced in the framework of the shell model, however, these calculations cannot describe the observed electric dipole excitations. The ${1/2}^{+}$ state at 3060 keV is proposed to be the weak coupling of an $f_{5/2}$ proton hole to the $3^{-}$ octupole vibrational state in the $N=50\mathrm{}$ core ${}^{88}\mathrm{Sr}.$ The relatively strong $E1\mathrm{}$ transition from that state to the ground state is explained as mainly the neutron $h_{11/2}\to g_{9/2}$ transition. The breakup of the $N=50\mathrm{}$ core and neutron excitations into the $h_{11/2}$ shell are essential to describe electric dipole excitations, but neutron-core excitations do not play an important role for the structure of magnetic dipole excitations.

The binding energy in nuclear matter is evaluated within the framework of self-consistent Green’s function theory, using a realistic nucleon-nucleon interaction. The two-body dynamics is solved at the level of summing particle-particle and hole-hole ladders. We go beyond the on-shell approximation and use intermediary propagators with a discrete-pole structure. A three-pole approximation is used, which provides a good representation of the quasiparticle excitations, as well as reproducing the zeroth- and first-order energy-weighted moments in both the nucleon removal and addition domains of the spectral function. Results for the binding energy are practically independent of the details of the discretization scheme. The main effect of the increased self-consistency is to introduce an additional density dependence, which causes a shift towards lower densities and smaller binding energies, as compared to a (continuous choice) Brueckner calculation with the same interaction. Particle number conservation and the Hugenholz–Van Hove theorem are satisfied with reasonable accuracy.

Xe isotopes near mass $A\sim 130$ region, which exhibit features of O(6) symmetry at low energy and the backbending at high spins, are studied in the shell model framework. The monopole and quadrupole pairing plus quadrupole-quadrupole interaction is employed as an effective interaction. As for single-particle levels, the ${1d}_{3/2},$ ${0h}_{11/2},$ ${2s}_{1/2}$ orbitals are taken into account for neutrons and the ${1d}_{5/2},$ ${0g}_{7/2}$ orbitals for protons under the assumption of $N=Z=64\mathrm{}$ subshell closure. The calculation reproduces the experimental energy levels of high-spin states as well as low-lying states well. This is the first successful microscopic description of the backbending in this mass region. The shell model states are examined in pair-truncated models. The analysis shows the alignment of two ${0h}_{11/2}$ neutrons at high spins.

For the first time evidence of the ground state of the proton-rich, unbound nucleus ${}^{10}\mathrm{N}$ has been found in the multinucleon transfer reaction ${}^{10}\mathrm{B}{(}^{14}\mathrm{N}{,}^{14}\mathrm{B}{)}^{10}\mathrm{N}.$ The observed resonance of ${}^{10}\mathrm{N}$ has a mass excess of 38.8(4) MeV and a width of $\Gamma =2.3\mathrm{}\left(16\right)\mathrm{}\hspace{0.5em}\mathrm{MeV},$ close to the Audi-Wapstra estimation of 38.5(4) MeV. ${}^{10}\mathrm{N}$ is the last missing $A=10\mathrm{}$ multiplet partner.

The particle-hole density matrix renormalization group $(p-h$ DMRG) method is discussed as a possible new approach to large-scale nuclear shell-model calculations. Following a general description of the method, we apply it to a class of problems involving many identical nucleons constrained to move in a single large j-shell and to interact via a pairing plus quadrupole interaction. A single-particle term that splits the shell into degenerate doublets is included so as to accommodate the physics of a Fermi surface in the problem. We apply the $p-h$ DMRG method to this test problem for two j values, one for which the shell model can be solved exactly and one for which the size of the Hamiltonian is much too large for exact treatment. In the former case, the method is able to reproduce the exact results for the ground state energy, the energies of low-lying excited states, and other observables with extreme precision. In the latter case, the results exhibit rapid exponential convergence, suggesting the great promise of this new methodology even for more realistic nuclear systems. We also compare the results of the test calculations with those from Hartree-Fock-Bogoliubov approximation and address several other questions about the $p-h$ DMRG method of relevance to its usefulness when treating more realistic nuclear systems.

The phenomenon of shape coexistence is studied in the relativistic Hartree-Bogoliubov framework. Standard relativistic mean-field effective interactions do not reproduce the ground-state properties of neutron-deficient Pt-Hg-Pb isotopes. It is shown that, in order to consistently describe binding energies, radii, and ground-state deformations of these nuclei, effective interactions have to be constructed, which take into account the sizes of spherical shell gaps.

In most cases shell-model calculations are not performed using Hartree-Fock self-consistency conditions. In calculations limited to the valence space, this may not lead to any problems, but when higher shell admixtures are allowed the calculated observables implicitly include Hartree-Fock terms that may be undesirable. In this work, we compare non-self-consistent and nearly self-consistent calculations of the spin-orbit splitting of the $p_{1/2}$ and $p_{3/2}$ hole states in $A=15.\mathrm{}$ We find that when higher shell admixtures $\left(2\mathrm{}ħ\omega \right)$ are included in the model space, and when a “standard” interaction is used, the spin-orbit splitting increases relative to a $0ħ\omega$ calculation. However, when the interaction and/or the kinetic energy are modified so as to achieve self-consistency the reverse is true, with the spin-orbit splitting in the $\mathrm{}(0+2)\mathrm{}ħ\omega$ space becoming smaller than that in the $0ħ\omega$ space. Furthermore, we show that self-consistency cannot be achieved by modifying the two-body spin-orbit or tensor terms, but is possible by adding a monopole-monopole term.

The particle emission at intermediate velocities in mass asymmetric reactions is studied within the framework of classical molecular dynamics. Two reactions in the Fermi energy domain were modeled, ${}^{58}\mathrm{N}\mathrm{i}+\mathrm{C}$ and ${}^{58}\mathrm{N}\mathrm{i}+\mathrm{A}\mathrm{u}$ at 34.5 MeV/nucleon. The availability of microscopic correlations at all times allowed a detailed study of the fragment formation process. Special attention was paid to the physical origin of fragments and emission timescales, which allowed us to disentangle the different processes involved in the midrapidity particle production. Consequently, a clear distinction between a prompt preequilibrium emission and a delayed aligned asymmetric breakup of the heavier partner of the reaction was achieved.

Selected results of a classical simulation of N particles in strong interaction are presented. The static properties of such classical systems are qualitatively similar to the known properties of atomic nuclei. The simulations of collisions show that all observed reaction mechanisms in nucleus-nucleus collisions are present in this numerical simulation. The first studies of such collisions are in qualitative agreement with experimental observations. This simulation could shed new light on energy deposition in heavy ion collisions: the excitation energy of each cluster is found to be lower than the energy of the least bound particle in the cluster. Finally, the similarities of fragmentation pattern with those obtained with a statistical code indicate that an unambiguous link can be established between the statistical and the dynamical descriptions of reaction mechanisms.

Angular distributions of the differential cross section for the ${}^{13}\mathrm{C}{\mathrm{}(d,p)\mathrm{}}^{14}\mathrm{C}$ reaction at 200–350 keV deuteron energies have been calculated using the finite range distorted wave Born approximation (DWBA) model and have been compared with the experimental data. Optical model parameters data used in the present DWBA model calculations, was taken from previous normalized zero-range DWBA calculations for the ${}^{13}\mathrm{C}{\mathrm{}(d,p)\mathrm{}}^{14}\mathrm{C}$ reaction at 410–810 keV deuteron energies. There is good agreement between the finite range DWBA model calculations and the experimental ${}^{13}\mathrm{C}{\mathrm{}(d,p)\mathrm{}}^{14}\mathrm{C}$ cross section data at 200–350 keV deuteron energies. For the sake of comparison, the angular distributions were also calculated using the zero-range DWBA approximation. It was observed that the differential cross section obtained from normalized zero-range calculations over 200–350 keV deuteron energies was about 30–40 % smaller than that obtained from finite range calculations. The study has shown that the ${}^{13}\mathrm{C}{\mathrm{}(d,p)\mathrm{}}^{14}\mathrm{C}$ reaction at such low deuteron energies still proceed through the direct reaction channel and can be explained using the finite-range DWBA model.

The interaction of ${}^8\mathrm{Li}$ with ${}^{208}\mathrm{Pb}$ has been studied over a range of energies near the nominal Coulomb barrier. An excitation function for the total reaction cross section is obtained from elastic-scattering angular distributions and compared with existing data for ${}^{6,7}\mathrm{Li}$ scattering. The result of this comparison indicates that the interaction barrier for ${}^8\mathrm{Li}{+}^{208}\mathrm{Pb}$ is reduced by approximately 4 MeV relative to that of ${}^7\mathrm{Li}.$ The yields of ${}^7\mathrm{Li}$ and ${}^4\mathrm{He}$ from breakup and/or transfer processes are determined, and compared with similar data for other light, weakly bound projectiles.

Enhancement of $\Omega$ and $\overline{\Omega }$ baryon production in Pb+Pb collisions at a center-of-mass energy of $17A\hspace{0.5em}\mathrm{GeV}$ can be explained by the formation of many small disoriented chiral condensate regions. This explanation implies that neutral and charged kaons as well as pions must exhibit novel isospin fluctuations. We compute the distribution of the fraction of neutral pions and kaons from such regions. We then propose robust statistical observables that can be used to extract the novel fluctuations from background contributions in ${\pi }^0{\pi }^{\pm }$ and $K_S^0{K}^{\pm }$ measurements at the Brookhaven Relativistic Heavy Ion Collider and the CERN Large Hadron Collider.

We reanalyzed the Wilkinson-Alburger delayed-α spectra from ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ decay, accounting for lepton-recoil broadening that had been neglected in previous analyses. This substantially improved the quality of the fits. The ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ delayed-α spectra are now consistently described by the same ${}^8\mathrm{Be}$ final-state continuum. In our analysis, which did not invoke a low-lying intruder state, the discrepancy between the final-state continua inferred from the delayed-α spectra and from the $L=2\mathrm{}$ α+α phase shifts is much less than found by previous authors. This largely resolves discrepancies noted by Barker and Warburton; the remaining differences may be artifacts of the assumption that the β-decay matrix elements are independent of excitation energy. Our analysis of the Wilkinson-Alburger data is consistent with results from the recent coincidence study of Ortiz et al., which gives additional confidence in using delayed-α spectra to infer the spectrum of ${}^8\mathrm{B}$ neutrinos that dominate the counting rate of many solar neutrino detectors.

We have studied the ${}^{29}\mathrm{Si}{(}^3\mathrm{He}{,}^6\mathrm{He}{)}^{26}\mathrm{Si}$ reaction and have identified new states in ${}^{26}\mathrm{Si}$ at $E_x=5.140\mathrm{}\left(10\right),$ $E_x=5.678\mathrm{}\left(8\right)\mathrm{}\hspace{0.5em}\mathrm{MeV},$ and $E_x=5.945\mathrm{}\left(8\right).$ Based on these measurements and other recent evidence, we suggest spin-parity assignments of $1^{+}$ for the 5.678 MeV state and $3^{+}$ for the 5.945 MeV state, which would account for all the “missing” unnatural parity states in ${}^{26}\mathrm{Si}$ in the excitation energy region important to hydrogen burning in novae. New reaction rates are presented for the ${}^{25}\mathrm{Al}(p,\gamma {)}^{26}\mathrm{Si}$ reaction based on this possible assignment of states.

The possibility of facing critical phenomena in nuclear fragmentation is a topic of great interest. Different observables have been proposed to identify such a behavior, in particular, some related to the use of information entropy as a possible signal of the critical behavior. In this work we critically examine some of the most widely used ones comparing its performance in bond percolation and in the analysis of fragmenting Lennard-Jones drops.

Neutron total reaction cross sections at 45, 50, 55, 60, 65, and 75 MeV from nuclei ${}^{12}\mathrm{C},$ ${}^{28}\mathrm{Si},$ ${}^{56}\mathrm{Fe},$ ${}^{90}\mathrm{Zr},$ and ${}^{208}\mathrm{Pb}$ have been measured and are compared with (microscopic) optical model predictions. The optical potentials were obtained in coordinate space by folding effective nucleon-nucleon interactions with realistic nuclear ground state density matrices. The agreement found is good to excellent.

Poincaré covariant Faddeev equations for the nucleon and $\Delta$ are solved to illustrate that an internally consistent description in terms of confined-quark and non-point-like confined-diquark correlations can be obtained. $\pi N$-loop induced self-energy corrections to the nucleon’s mass are analyzed and shown to be independent of whether a pseudoscalar or pseudovector coupling is used. Phenomenological constraints suggest that this self-energy correction reduces the nucleon’s mass by up to several hundred MeV. That effect does not qualitatively alter the picture, suggested by the Faddeev equation, that baryons are quark-diquark composites. However, neglecting the $\pi$ loops leads to a quantitative overestimate of the nucleon’s axial-vector diquark component.

High-spin states have been studied in neutron-deficient ${}_{\hspace{0.5em}54}^{114}\mathrm{Xe},$ populated through the ${}^{58}\mathrm{Ni}{(}^{58}\mathrm{Ni},2p)$ fusion-evaporation reaction at 230 MeV. The Gammasphere $\gamma$-ray spectrometer has been used in conjunction with the Microball charged-particle detector in order to select evaporation residues of interest. The yrast band has been greatly extended to a tentative spin of $52ħ$ and shows features consistent with smooth band termination. This band represents the first evidence for a core-excited (six-particle, two-hole) proton configuration above $Z=53.\mathrm{}$

The momentum widths of the primary fragments and observed final fragments have been investigated within the framework of an antisymmetrized molecular dynamics transport model code with a sequential decay afterburner (GEMINI). It is found that the secondary evaporation effects cause the values of a reduced momentum width ${\sigma }_0,$ derived from momentum widths of the final fragments, to be significantly less than those appropriate for the primary fragment but close to those observed in many experiments. Therefore, a new interpretation for experimental momentum widths of projectilelike fragments is presented.

Angular distributions of fluorine and oxygen produced from $170\hspace{0.5em}\mathrm{MeV}$ ${}^{17}\mathrm{F}$ incident on ${}^{208}\mathrm{Pb}$ were measured. The elastic scattering data are in good agreement with optical model calculations using a double-folding potential and parameters similar to those obtained from ${}^{16}\mathrm{O}{+}^{208}\mathrm{Pb}.$ A large yield of oxygen was observed near ${\theta }_{\mathrm{lab}}=36\mathrm{}°.$ It is reproduced fairly well by a calculation of the ${(}^{17}\mathrm{F}{,}^{16}\mathrm{O})$ breakup, which is dominated by one-proton stripping reactions. The discrepancy between our previous coincidence measurement and theoretical predictions was resolved by including core absorption in the present calculation.