Coherent η-meson photoproduction on the deuteron has been studied, where the emphasis is on the relative importance of two-body contributions from hadronic rescattering and electromagnetic meson exchange currents besides the impulse approximation. For the elementary photoproduction amplitude a coupled resonance model developed by Bennhold and Tanabe has been used that fits reasonably well with the experimental data. The rescattering effects are treated within a coupled channel approach considering the intermediate excitation of the $P_{11}\mathrm{}\left(1440\right),$ $D_{13}\mathrm{}\left(1520\right),$ and $S_{11}\mathrm{}\left(1535\right)\mathrm{}$ nucleon resonances. The hadronic interaction between nucleon and resonances is modeled by one-boson exchange potentials, which we have considered both in the static approximation as well as fully retarded. The sum of all considered two-body effects results in an enhancement of the total cross section between 10 in the maximum and $25\%$ closer to threshold around 680 MeV if the hadronic interaction is treated retarded. This enhancement shows up in the differential cross sections mainly at backward angles. It increases steadily from only a few percent at $0°$ to more than a factor of 2 at $180°$ for a photon energy of 680 MeV. Two-body effects also become significant in certain polarization observables. Finally, no discrepancy has been found for the ratio of the isoscalar amplitude to the proton amplitude between coherent and incoherent $\eta$ photoproduction on the deuteron due to a nonvanishing complex and energy dependent phase relation.

We explore the role of coupling to $\Delta$ isobars (in both the $N\Delta$ and $\Delta \Delta$ channels) in medium modifications of the effective $\mathrm{NN}$ interaction that drives 200-MeV proton inelastic scattering. A comparison of the predictions to natural-parity ${(p,p}^{\prime })$ cross section and analyzing power data show that isobar degrees of freedom in the medium generate overly repulsive effective interactions. Furthermore, this model extension is unable to resolve difficulties observed earlier describing polarization transfer measurements in some high-spin, unnatural-parity ${(p,p}^{\prime })$ transitions.

The high-spin decay scheme of ${}^{155}\mathrm{Er},$ known previously, has been considerably extended by using the EUROGAM II γ-ray array. The so-called quasi-isotropic gating data-analysis method, capable of providing spin and parity assignments with triple or quadruple coincidence data has been used. With such coincidence information, we have determined γ-ray angular distributions, DCO ratios, and linear polarizations for many of the observed transitions. The level scheme is interpreted by using the particle-hole analysis based on the deformed Woods-Saxon potential and the monopole pairing interaction. The results indicate that at $\sim 12.3$ MeV excitation energy, all nine valence particles around the ${}_{64}^{146}{\mathrm{Gd}}_{82}$ core exhaust the maximum spin of $I=79/2\mathrm{}ħ.$ At higher spin, relatively high-energy transitions, of the order of $\sim 1.5$ MeV, related to the breaking of the proton or neutron cores are observed. According to the calculations, this corresponds to an oblate-shape polarization of the nucleus with quadrupole deformation ${\beta }_2\sim -\mathrm{0.12.}$

The density dependent relativistic hadron field (DDRH) theory is applied to strongly asymmetric nuclear matter and finite nuclei far off stability. A new set of in-medium meson-nucleon vertices is derived from Dirac-Brueckner Hartree-Fock (DBHF) calculations in asymmetric matter, now accounting also for the density dependence of isovector coupling constants. The scalar-isovector δ meson is included. Nuclear matter calculations show that it is necessary to introduce a momentum correction in the extraction of coupling constants from the DBHF self-energies in order to reproduce the DBHF equation of state by DDRH mean-field calculations. The properties of DDRH vertices derived from the Groningen and the Bonn-A nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ potentials are compared in nuclear matter calculations and for finite nuclei. Relativistic Hartree results for binding energies, charge radii, separation energies, and shell gaps for the Ni and Sn isotopic chains are presented. Using the momentum corrected vertices an overall agreement to data on a level of a few percent is obtained. In the accessible range of asymmetries the δ meson contributions to the self-energies are found to be of minor importance but asymmetry dependent fluctuations may occur.

The 270-MeV ${}^{58}\mathrm{Ni}+$${}^{102}\mathrm{Pd}$ reaction was used for the first recoil-decay tagging measurement with Gammasphere coupled to the Fragment Mass Analyzer at Argonne National Laboratory. Level structures of ${}^{155}\mathrm{Yb},$ ${}^{156}\mathrm{Lu},$ and ${}^{157}\mathrm{Lu},$ as well as the excited states associated with the ${25/2}^{-}$ isomer in ${}^{155}\mathrm{Lu},$ are identified for the first time. The systematical behavior of the energy levels is compared with that of neighboring isotones and isotopes. The attractive interaction between $h_{11/2}$ protons and $h_{9/2}$ neutrons plays an important role in the structure of ${}^{155}\mathrm{Yb}$ and ${}^{155,156}\mathrm{Lu}.$

Lifetimes of eight high spin states were measured in the yrast band of even-even nucleus ${}^{80}\mathrm{Kr}$ by Doppler shift attenuation method. High spin states were populated by the heavy ion fusion evaporation reaction ${}^{65}\mathrm{Cu}{(}^{19}\mathrm{F}{,2p2n)}^{80}\mathrm{Kr}.$ The transition quadrupole moments, extracted from the lifetimes of the states, show a decreasing tendency after the band crossing indicating a change in shape of ${}^{80}\mathrm{Kr}$ at high spin. The total Routhian surface calculations, using Woods-Saxon mean field potential and BCS pairing with Strutinsky shell correction procedure, predict a change from a near oblate to near prolate shape with small deformation along the yrast band at high spin in ${}^{80}\mathrm{Kr}.$ The present experimental $Q_t$ values and the second alignment in the yrast band of ${}^{80}\mathrm{Kr}$ support the predicted change in shape.

A particle-vibration coupling model is applied to explain the spectroscopic factors and decay rates of odd-$A$ and odd-odd near-spherical proton emitters, as well as the branching ratio for the recently observed fine structure in the decay of ${}^{145}\mathrm{Tm}.$ In addition, a deformed solution for ${}^{145}\mathrm{Tm}$ with ${K=5/2\mathrm{}}^{-}$ is presented. Using particle-vibration coupling, good agreement is achieved with observed spectroscopic factors for the near-spherical emitters, including $d_{3/2}$ cases. For the odd-odd emitters, the unpaired neutron is treated as a spectator. The single-particle potential used in this work has the same parameters as that used to successfully describe the decay rates of the deformed proton emitters ${}^{131}\mathrm{Eu}$ and ${}^{141}\mathrm{Ho}.$

We investigate the validity of the method of computing ground-state energies, at a given angular momentum, with Monte Carlo methods applied to the functional integral formulation containing pairing fields. Calculations have been performed for several erbium isotopes and a few dysprosium isotopes. It is found that some residual sign fluctuations, which seem to be associated with a small neutron number above the $N=82\mathrm{}$ shell closure, are present, but that they do not affect the feasibility of the calculations. Such sign fluctuations disappear as the neutron number is increased. Also, an efficient improved method for the computation of the functional integral in the case of an odd number of particles is presented. The Monte Carlo method of Metropolis et al. [J. Chem. Phys. 21, 1087 (1953)] is used in the evaluation of expectation values.

A simple model based on the canonical-ensemble theory is outlined for hot nuclei. The properties of the model are discussed with respect to the Fermi gas model and the breaking of Cooper pairs. The model describes well the experimental level density of deformed nuclei in various mass regions. The origin of the so-called S shape of the heat capacity curve $C_V\mathrm{}\left(T\right)\mathrm{}$ is discussed.

The g factor of the first $2^{+}$ state of ${}^{54}\mathrm{Cr}$ was remeasured employing the combined technique of projectile Coulomb excitation in inverse kinematics and transient magnetic fields. The value obtained, $g=+0.840\mathrm{}\left(56\right),$ is significantly larger than previous data. The new value agrees better with a truncated than with a large-scale shell model calculation. The present result is discussed in the context of recently determined g factors of the first $2^{+}$ states of ${}^{50}\mathrm{Cr}$ and ${}^{52}\mathrm{Cr}$ as well as $B\left(E2\mathrm{}\right)\mathrm{}$ values determined from lifetime measurements.

The double differential cross sections of neutron production from thin C, Al, Cu, and Pb targets bombarded by 135 MeV/nucleon He, C, and Ne ions and by 95 MeV/nucleon Ar ion were measured using the RIKEN Ring Cyclotron of the Institute of Physical and Chemical Research, Japan. The neutron energy spectra at 0°, 15°, 30°, 50°, 80°, and 110° were obtained by using the time-of-flight method. The neutron spectra in the forward direction have a sharp peak that is located at the incident particle energy per nucleon due to the knockon process, and spreads out to about three times the incident particle energy per nucleon. The resultant spectra were integrated over energy to produce neutron angular distributions. The total neutron production cross sections were obtained by integrating over the angular distributions. The experimental results are compared with calculations using the intranuclear cascade-evaporation Monte Carlo code HIC and the quantum molecular dynamics code QMD.

Quasielastic scattering cross sections have been measured with a $950\mathrm{MeV}/c$ ${\pi }^{-}$ beam on targets of ${}^2\mathrm{H},$ ${}^6\mathrm{Li},$ C, Ca, Zr, and ${}^{208}\mathrm{Pb},$ over a range of three-momentum transfers from 350 through $650\mathrm{MeV}/c.\mathrm{}$ Results for carbon are compared to a finite-nucleus continuum random-phase approximation calculation including distortions. The pion spectra at our lowest range of momentum transfers show less scalar/isoscalar correlation than predicted.

In-plane and out-of-plane angular correlations of fission fragments detected in coincidence with projectile residues produced in nuclear collisions ${}^{19}{\mathrm{F}+}^{238}\mathrm{U}$ at 115, 120, and 125 MeV have been investigated. The data are described assuming sequential fission decay of targetlike nuclei produced in peripheral transfer reactions.

Nucleon electromagnetic form factor data (including recent data) is fitted with models that respect the confinement and asymptotic freedom properties of QCD. Gari-Krümpelmann (GK) type models, which include the major vector meson pole contributions and at high momentum transfer conform to the predictions of perturbative QCD, are combined with Höhler-Pietarinen (HP) models, which also include the width of the $\rho$ meson and the addition of higher mass vector meson exchanges, but do not evolve into the explicit form of PQCD at high momentum transfer. Different parametrizations of the GK model’s hadronic form factors, the effect of including the width of the $\rho$ meson, and the addition of the next (in mass) isospin 1 vector meson are considered. The quality of fit and the consistency of the parameters select three of the combined HP/GK type models. Projections are made to the higher momentum transfers which are relevant to electron-deuteron experiments. The projections vary little for the preferred models, removing much of the ambiguity in electron-nucleus scattering predictions.

The half-life of ${}^{130}\mathrm{Ba}$ due to multichannel weak decay $(2\mathrm{}{\beta }^{+},$ 2EC, and $\mathrm{EC}{\beta }^{+})$ has been determined for the first time by the measurement of the ${}^{130}\mathrm{Xe}$ daughter accumulated in natural barite $\left({\mathrm{BaSO}}_4\right)$ from the Belorechenskoe deposit in North Caucasus, Russia. The accumulation time was determined from U-Xe and K-Ar gas-retention ages measured in the same material, yielding a half-life for ${}^{130}\mathrm{Ba}$ for all weak decay modes of $2.2\pm 0.5\times {10}^{21}\mathrm{yr}$ (68% C.L.), about a factor of 2 lower than that predicted by the proton-neutron quasiparticle random phase approximation. From excess ${}^{132}\mathrm{Xe}$ observed in this barite, the half-life for weak decay of ${}^{132}\mathrm{Ba}$ can be estimated ${(T}_{1/2}=1.3\mathrm{}\pm 0.9\times {10}^{21}\mathrm{yr}).\mathrm{}$ However, this value is more tentative, since other sources of this isotope cannot be excluded, but the lower limit of $2.2\times {10}^{21}\mathrm{yr}$ remains firm.

We explore changes in abundance patterns that occur late in the r process. As the neutrons available for capture begin to disappear, a quasiequilibrium funnel shifts material into the large peaks at $A=130\mathrm{}$ and $A=195,$ and into the rare-earth “bump” at $A=160.\mathrm{}$ A bit later, after the free-neutron abundance has dropped and beta decay has begun to compete seriously with neutron capture, the peaks can widen. The degree of widening depends largely on neutron-capture rates in a few nuclei near closed neutron shells and relatively close to stability. We identify particular nuclei whose capture rates should be examined experimentally, perhaps at a radioactive beam facility.

The multipole mixing ratios of $\gamma$ transitions among the low-spin states of ${}^{130}\mathrm{Ba}$ have been studied by means of a $\gamma \gamma$ angular correlation analysis. The excited states of ${}^{130}\mathrm{Ba}$ were populated in the $\beta$ decay of ${}^{130}\mathrm{La}$ obtained with the ${}^{120}\mathrm{Sn}{(}^{14}\mathrm{N},4n)$ reaction at 65 MeV. The $\gamma$ ray spectra were measured off-beam with the Osiris-8 detector array, which was enhanced by one Euroball cluster detector, at the University of Cologne. We obtained precise and unique values for the multipole mixing ratios of 18 transitions.

The nucleon-pair shell model truncated to the $S-D$ subspace is applied to nucleus ${}^{134}\mathrm{Ba}$ for examining the effects on collectivity due to long-range $n-p$ quadrupole forces. It is found that symmetric and mixed-symmetric states, consequently $M1\mathrm{}$ transitions, are primarily controlled by the $n-p$ quadrupole interaction. In comparison with surface-$\delta$ interaction, when the quadrupole $n-p$ coupling is weak, the model can produce approximately the vibrational limit, and when the quadrupole $n-p$ coupling is strong, the O(6) limit can be realized.

The quark-meson coupling model for a nucleon is considered. The model describes a nucleon as an MIT bag, in which quarks are coupled to scalar and vector mesons. A set of coupled equations for the quark and the meson fields are obtained and are solved in a self-consistent manner. It is shown that the mass of a nucleon as a dressed MIT bag interacting with $\sigma$- and $\omega$-meson fields significantly differs from the mass of a free MIT bag. A few sets of model parameters are obtained so that the mass of a dressed MIT bag becomes the nucleon mass. The results of our calculations imply that the self-energy of the bag in the quark-meson coupling model is significant and needs to be considered in doing the nuclear matter calculations.