The optical relativistic model based on deep attractive forbidden state quasipotentials describes well the angular and energy dependence of differential np- and pp-scattering cross sections and polarizations, including the transition from the U-shaped form of the angular distributions of np scattering to forward scattering at the energy ${\mathit{E}}_{\mathrm{lab}}$≥1 GeV, when the scattering P-phase shifts, equal to π at low energies, pass through π/2 (the triplet and singlet S-phase shifts start from the values 2π and π, respectively). The higher scattering phase shifts (L≥2) are small everywhere. The potentials are determined from the scattering phase shifts in the low-energy region ${\mathit{E}}_{\mathrm{lab}}$<1 GeV. They have been chosen in the simple Gaussian form and for different partial waves they differ in depth and width (from ${\mathit{V}}_0$=0.73 GeV, a=0.85 fm to ${\mathit{V}}_0$=2.40 GeV, a=0.45 fm). A few negative phase shifts ${}_{}{}^3{}_{}{}^{}$${\mathit{D}}_1$, ${}_{}{}^3{}_{}{}^{}$${\mathit{F}}_3$, ${}_{}{}^3{}_{}{}^{}$${\mathit{G}}_3$, which reflect the peripheral repulsion due to the spin-orbital and tensor interactions, are calculated by means of the one-boson-exchange potential periphery matched to the central attraction. The imaginary part W of the optical potential V+iW is determined by the value ${\mathrm{\sigma }}_{\mathrm{tot}}$/${\mathrm{\sigma }}_{\mathrm{el}}$ and grows rapidly with increase in the energy ${\mathit{E}}_{\mathrm{lab}}$, so that the phase-shift values lose sensitivity to the real part V of optical potential if ${\mathit{E}}_{\mathrm{lab}}$ exceeds 5 GeV. Finally, the quantum chromodynamics (QCD) effects are discussed which may underlie the potentials considered.

We study the isospin dependence of nucleon-nucleon potentials by examining solutions to the Schrödinger equation in paronic (Pauli-forbidden) states. We find a model dependence to the isovector content and discuss its origin. We observe a qualitative difference between meson-exchange-based models and those that are more phenomenological. This has consequences for a number of issues of current interest.

We report differential cross-section measurements at up to 16 angles for the reaction ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$(α,${\mathrm{\alpha }}_0$${)}^{20}$Ne for 3.8≤${\mathit{E}}_{\mathrm{\alpha }}$≤11 MeV in steps ≤15 keV. The target was a differentially pumped windowless gas target of high-purity Ne, buffered by He to reduce the rate of Ne outflow. A total of 39 levels in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ (12.5<${\mathit{E}}_{\mathit{x}}$<18.2 MeV) were analyzed by writing the reaction amplitude for spinless positive-parity particles as a nonresonant term which varies linearly with energy plus a sum over only resonant partial waves. In addition, 56 other levels and 22 possible levels were also identified over the same energy region.

High-spin states in ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ have been studied by in-beam, gamma-ray spectroscopy. In ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ the three known bands beginning at $8^{+}$ are found to exhibit crossing transitions and other new positive-parity bands are discovered to feed into them. In ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ only a single positive-parity yrast band is seen to high spin. Detailed, more realistic microscopic model calculations have been carried out for ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$. There is striking agreement between the calculations and the new data for ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$, including a predicted new band with superdeformation, β∼0.42. The calculations for ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ predict similar multiple band structures that are not seen experimentally.

Differential cross sections are reported for elastic scattering and for exciting the $2_1^{+}$ (1.81 MeV), $2_2^{+}$ (2.94 MeV), $4_1^{+}$ (4.32 MeV), and the $4_2^{+}$ (4.90 MeV) states of ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ from ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ (200 MeV)${+}^{208}$Pb scattering. In addition, we have measured complete particle-γ angular correlations for the $2_1^{+}$→$0_1^{+}$, $2_2^{+}$→$2_1^{+}$, and $4_2^{+}$→$2_1^{+}$ γ decays. Coupled-channels analysis was performed to extract E2 and E4 matrix elements. For the ground-state rotational band we find M(E2;$0_1^{+}$⇆$2_1^{+}$)=-16.79±0.13 e ${\mathrm{fm}}^2$, M(E4;$0_1^{+}$⇆$4_2^{+}$)=+95±10 e ${\mathrm{fm}}^4$, and ${\mathit{Q}}_2$($2_1^{+}$)=-20.9±1.9 ${\mathrm{fm}}^2$, where we have identified the $4_2^{+}$ (4.90 MeV) state as a member of the ground-state band rather than the $4_1^{+}$ (4.32 MeV) state. The $2_2^{+}$ (2.94 MeV) state is not well accounted for by the asymmetric-rotor model.

The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(n,p${)}^{16}$N reaction was measured at an incident neutron energy of 298 MeV at average center-of-mass angles of 2.0°, 6.5°, and 10.6°. The Gamow-Teller (GT) and spin-dipole strength functions were extracted using a multipole decomposition technique with theoretical angular distributions with L transfers of 0, 1, and 2 from distorted-wave impulse-approximation (DWIA) calculations. The extracted strengths are compared to distributions expected from shell-model calculations which include 2ħω and 4ħω excitations. The pure spin-dipole multiplet at 0.2 MeV excitation shows a different shape than the angular distribution from the DWIA calculations, which may affect the amount of GT strength extracted from the multipole decomposition.

The quadrupole moments of the isomeric (π${\mathit{h}}_{9/2}$ν${\mathit{i}}_{13/2}^{\mathrm{-}1}$) configurations in ${}_{}{}^{202,204,206,207}{}_{}{}^{}\mathrm{Bi}$ are measured by the level-mixing-spectroscopy method. They are very small, but show a large relative increase as more neutrons are removed from the closed N=126 shell. In addition, the temperature-dependent electric-field gradient and relaxation time of BiTl are measured. The multipolarity mixing of the 675 keV in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Bi}$ is corrected.

Quadrupole moments of six high-spin isomers in the At isotopes have been measured with the level-mixing-spectroscopy method: ${}_{}{}^{208}{}_{}{}^{}\mathrm{At}$(${16}^{\mathrm{-}}$), ${}_{}{}^{209}{}_{}{}^{}\mathrm{At}$(29/$2^{+}$), ${}_{}{}^{210}{}_{}{}^{}\mathrm{At}$(${19}^{+}$,${15}^{\mathrm{-}}$), ${}_{}{}^{211}{}_{}{}^{}\mathrm{At}$(39/$2^{\mathrm{-}}$,29/$2^{+}$). The results show that level mixing spectroscopy is a promising technique to determine quadrupole moments of isomers that are difficult to measure by other in-beam hyperfine interaction methods. A large increase of the quadrupole moment is observed if neutrons are excited across or removed from the N=126 shell closure. This behavior is explained in terms of an enhanced core softness for fewer core neutrons; the aligned valence particles, moving in equatorial orbits, then easily polarize the core towards oblate deformation.

The (p→,α) reaction on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ has been studied at an incident proton energy of 22 MeV using a polarized proton source and a spectrometer. The angular distributions and the asymmetries for transitions to levels of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ up to an excitation energy of 3 MeV have been measured. The analysis of these data by means of the finite-range distorted-wave Born approximation theory using either conventional Woods-Saxon and double-folded α-particle potentials has allowed us to make several new attributions of spin and parity.

Directional correlations of coincident gamma transitions have been measured in ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$ following the ${\mathrm{\beta }}^{\mathrm{-}}$ decay of fission product ${}_{}{}^{135}{}_{}{}^{}\mathrm{I}$ (${\mathit{T}}_{1/2}$=6.7 h) using a spectrometer consisting of a Ge and a Ge(Li) detector. The measurements were carried out for 14 gamma cascades populated in ${}_{}{}^{135}{}_{}{}^{}\mathrm{Xe}$. The present results permitted definite spin assignment to the levels at 1131 keV (7/$2^{+}$), 1678 keV (7/$2^{+}$), 1968 keV (9/$2^{+}$), 2223 keV (9/$2^{+}$), 2255 keV (7/$2^{+}$), and 2372 keV (9/2). In addition, several previous spin assignments to other levels were confirmed. The multipole mixing ratios δ(E2/M1) for 12 γ ray transitions were determined from the present results.

The decay of low- and high-spin isomers of ${}_{}{}^{102}{}_{}{}^{}\mathrm{Y}$ to levels in highly deformed ${}_{}{}^{102}{}_{}{}^{}\mathrm{Zr}$ was studied from mass-separated activity produced by thermal neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$. Based on γ singles and coincidence measurements, decay schemes for both isomers are deduced. Of special interest are states observed at 894 and 1211 keV that are postulated to be $0_2^{+}$ and $2_2^{+}$, respectively. Possible interpretations of these newly observed levels in terms of β, γ, or spherical bands are given.

The ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ decay of ${}_{}{}^{222}{}_{}{}^{}\mathrm{Ra}$ has been reinvestigated, using an 85 MBq activity ${}_{}{}^{230}{}_{}{}^{}\mathrm{U}$ source radiochemically separated, a Si barrier detector, and a superconducting magnetic spectrometer. In a 16 days counting run, 210 ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ events were recorded. The ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ particles energy value 30.930±0.090 MeV was found and an upper limit b≤2×${10}^{\mathrm{-}12}$ was estimated for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ branching ratio to the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ first excited state; the branching-ratio value to the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ ground state, thus equal to the total branching ratio, was found to be b=${\lambda }_{\mathit{c}}$/${\lambda }_{\mathrm{\alpha }}$=(2.31±0.31)×${10}^{\mathrm{-}10}$.

The saturation curve of symmetric nuclear matter is calculated at the Brueckner-Hartree-Fock level of approximation within the continuous choice for the single-particle potential. The realistic local Argonne ${\mathit{v}}_{14}$ potential is used and the results are compared with similar calculations presented in the literature. The binding energies per nucleon around saturation agree closely with previous results obtained with separable versions of the same potential as well as of the Paris potential.

An analysis of both the positive- and negative-parity states in the odd-mass Ba isotopes 121 to 131 is made within the framework of multishell interacting boson-fermion model calculations. Excitation energies and electromagnetic properties of low- and medium-spin levels are discussed in connection with their possible structure.

The systematics of the giant monopole resonance in even-mass Sn isotopes have been studied in the framework of the quasiparticle random-phase approximation. The effect of the inclusion of pairing correlations on the properties of the giant monopole and giant quadrupole resonances in superfluid Sn nuclei has been evaluated. A shift in the monopole energies of these nuclei by about 100–150 keV has been observed. It is shown that the shift in the energy of the breathing mode of finite superfluid nuclei influences the extraction of the nuclear matter compressibility from empirical data only minimally.

We calculate the pion propagator in nuclear matter in a relativistic random-phase approximation to the Walecka model. We present results for the pion dimesic function for densities up to several times normal nuclear matter density. We do not observe pion condensation even in the absence of short-range correlations. Although we do observe strong pionic enhancements, these enhancements disappear at high enough nuclear density due to the strong density dependence of the effective nucleon mass ${\mathit{M}}^{\mathrm{*}}$. For a set of parameters that give a smoother behavior of ${\mathit{M}}^{\mathrm{*}}$ with density there is a lower critical density for pion condensation to set in. In contrast to nonrelativistic calculations, however, there is also an upper critical density at which the normal state is restored.

We study the classical dynamical behavior of a family of Hamiltonians in the interacting boson model which describe the low-lying collective states of even-even nuclei. Two measures of classical chaos, the fractional volume of chaotic trajectories and the average largest Lyapunov exponent, are studied as a function of energy, angular momentum, and a parameter which interpolates between rotational and γ-unstable nuclei. Near these two limits the dynamics is regular but in the transition region it becomes chaotic. The results agree with a previous study of quantum chaos in the corresponding quantal model, where spectral and E(2) intensity fluctuations were analyzed. Contrary to most previous numerical studies which were restricted to unrealistic models in two degrees of freedom, the present model is realistic and has five degrees of freedom. The latter correspond to the five quadrupole nuclear shape degrees of freedom.

The nonphysical effects due to the false components introduced by the nonconservation of the particle number in the BCS states are eliminated in the theoretical values of the moment of inertia calculated by the microscopic cranking model. The states of the system are obtained by successive projections of the BCS states in the occupation number space. The moment of inertia appears then as a limit of a rapidly convergent sequence. The errors due to this false component have been numerically estimated and appear to be important both in the BCS states and in the matrix elements of the angular momentum. The predicted values of the moment of inertia satisfactorily reproduce the experimental data over a large number of nuclei within rare-earth and actinide regions with discrepancies ranging from 0.1% to 8%.

The energy levels of negative-parity states of even-even isotopes ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{158}{}_{}{}^{}\mathrm{Er}$, and ${}_{}{}^{164}{}_{}{}^{}\mathrm{Er}$ are studied in terms of the interacting s-, d-, and f-boson-approximation model and allowing one s or d boson to break and form a fermion pair. In the calculation two single fermion orbits ${\mathit{h}}_{11/2}$ and ${\mathit{i}}_{13/2}$ are considered. The energy levels of the negative-parity bands of these nuclei can be reproduced satisfactorily.

A derivation for reducing the adiabatic time-dependent Hartree-Fock theory with the consistency condition to an efficacious form, in which the evolution of the single-particle states is given by a time-dependent Hartree-Fock-like equation while the consistency condition is given by a one-body equation, is discussed. The density-dependent Skyrme interaction is included in the derivation.