Variational Monte Carlo calculations have been made for the ${}_{\mathrm{\Lambda }}{}^{17}{}_{}{}^{}\mathrm{O}$ hypernucleus using realistic two- and three-baryon interactions. A two-pion exchange potential with spin- and space-exchange components is used for the ΛN potential. Three-body two-pion exchange and strongly repulsive dispersive ΛNN interactions are also included. The trial wave function is constructed from pair- and triplet-correlation operators acting on a single-particle determinant. These operators consist of central, spin, isospin, tensor, and three-baryon potential components. A cluster Monte Carlo method is developed for noncentral correlations and is used with up to four-baryon clusters in our calculations. The three-baryon ΛNN force is discussed.

Benchmark solutions for three-nucleon breakup amplitudes in n-d scattering have been produced by two groups separately using momentum space and configuration space techniques. These results have been obtained at two energies for both spin doublet and quartet configurations for an s-wave potential model and are in excellent agreement.

A model for the nucleon-antinucleon interaction is presented which is based on meson-baryon dynamics. The elastic part is the G-parity transform of the Bonn NN potential. Annihilation into two mesons is described in terms of microscopic baryon-exchange processes including all possible combinations of π,η,ρ,ω,${\mathit{a}}_0$,${\mathit{f}}_0$,${\mathit{a}}_1$,${\mathit{f}}_1$,${\mathit{a}}_2$,${\mathit{f}}_2$,K,${\mathit{K}}^{\mathrm{*}}$. The remaining annihilation part is taken into account by a phenomenological energy- and state-independent optical potential of Gaussian form. The model enables a simultaneous description of nucleon-antinucleon scattering and annihilation phenomena with fair quality.

The neutron spectroscopy of the β-delayed neutron decay of ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ has been investigated. Two neutron groups were observed, and energy limits are given for a third (unobserved) group that receives most of the β-decay strength. Branching ratios and logft values deduced for all three groups are compared with the results of a shell-model calculation.

The magnetic moment of the first excited, 3/$2^{+}$ state of ${}_{}{}^{99}{}_{}{}^{}\mathrm{Zr}$ was measured using the integral perturbed angular correlation method, in an external magnetic field of 6.25 T. The result, g(3/$2^{+}$)=+0.28(4), is discussed in relation to theoretical calculations for spherical nuclei and also compared to predictions of the core-excitation model.

The ridge structure with Δ${\mathit{E}}_{\gamma }$=±30 keV, recently observed in the reaction 187 MeV ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$${+}^{120}$Sn and attributed to a hyperdeformed nuclear shape, has been confirmed in a new proton-γ coincidence experiment and assigned to the ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ nucleus. Estimates of the cross section for the population of the 30 keV ridge and for the associated entry states have been obtained. The proton spectra in coincidence with γ rays of different Dy isotopes show effects related to the exit channel and to the angular momentum but they are scarcely sensitive to the selection of different shapes (oblate, normal deformed prolate, superdeformed) in the same residual nucleus ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$. The energy of the protons in coincidence with the Δ${\mathit{E}}_{\gamma }$=±30 keV ridge is however larger than expected. This effect is discussed in the framework of the fission-evaporation competition.

Excited states of the neutron deficient nucleus ${}_{}{}^{109}{}_{}{}^{}\mathrm{Te}$ were identified for the first time in the ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$${(}^{58}$Ni,2pn) reaction by in-beam γ-spectroscopic methods. The nordball detector array, equipped with a charged-particle and a neutron detector system for reaction channel identification, was used to detect the evaporated particles and γ rays. A level scheme was constructed on the basis of γγ-coincidence relations, and the angular momenta of the states were determined from the measured angular correlation intensity ratios. Two favored bands built on the ν${\mathit{g}}_{7/2}$ and ν${\mathit{h}}_{11/2}$ neutron quasiparticle states were identified. The structure of the nucleus is discussed in the framework of the particle-vibration coupling model using the interacting boson-fermion formalism up to spin 27/2. The negative parity sequence is compared to Total Routhian Surface calculations.

A new superdeformed band has been identified in ${}_{}{}^{191}{}_{}{}^{}\mathrm{Hg}$ bringing the total number of bands observed in this nucleus to four. The new band has properties similar to those of a superdeformed band reported recently in ${}_{}{}^{193}{}_{}{}^{}\mathrm{Hg}$. Both bands are believed to be built on the unfavored signature of the ${\mathit{j}}_{15/2}$ intruder configuration. Comparisons between the data and cranked Woods-Saxon calculations highlight the strengths and weaknesses of theory in describing high-N orbitals at large deformation.

Electron scattering measurements have been made in order to determine the longitudinal and transverse form factors of low-lying level in ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$. With the exception of the broad 5.18 MeV level, results were obtained for all known levels up to 6.7 MeV. The measurements span the momentum transfer range q=0.48–2.58 ${\mathrm{fm}}^{\mathrm{-}1}$. The primary objective of this work was to improve the data on the pure isovector M3 form factor of the 1.740 MeV excitation, the transform of which yields the 1${\mathit{p}}_{3/2}$ single-nucleon wave function. A Woods-Saxon potential was found to provide a much better representation of the data than the harmonic oscillator model, and the rms size of this orbit was determined to be 2.79±0.11 fm in the relative core-particle coordinate frame. Nevertheless, confidence in the quantitative details of this interpretation is hindered by conflicting evidence regarding the contribution of core polarization. Our analysis of the Coulomb elastic form factor gave an rms radius for the ground-state charge distribution equal to 2.58±0.05±0.05 fm, slightly larger than values previously published. Longitudinal and transverse form factors deduced for inelastic transitions were compared with theoretical results of conventional 1p-shell models, models with 1ħω and 2ħω configurations involving the 1s, 2s1d, and 2p1f shells, and finally, a model that included core polarization. Although restricted 1p-shell models were found to provide good predictions for the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ natural-parity level spectrum and transverse form factors, they were less successful for C2 form factors: not only is there a considerable dependence on the 1p-shell interaction, but these models give just 45% of the total observed C2 transition strength. Only a 10% improvement was realized by expanding the shell model space to include 2ħω configurations. The inclusion of even higher-excited configurations by means of core polarization calculations was essential to remove the remaining shortfall.

High spin states in ${}_{}{}^{113}{}_{}{}^{}\mathrm{I}$ were studied with the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^{58}$Ni, 3pγ) reaction at 240 MeV, using the eurogam array in Daresbury, United Kingdom, with 45 Ge detectors. A total of five deformed intruder bands extending to spins I ranging from (73/2–89/2)ħ have been identified, all of which reach frequencies ħω>1.0 MeV and excitation energies ∼25 MeV. A gradual dropoff of the dynamic moment of inertia ${\mathit{scrI}}^{\mathrm{}\left(2\right)\mathrm{}}$ with increasing rotational frequency has been observed and attributed to a mode of ‘‘soft’’ band termination involving valence particle alignment. In this process, the nucleus progresses gradually, over many transitions, towards a noncollective oblate (γ=+60°) band terminating state.

The lifetimes in the decay of compound nuclei formed in the fusion reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ → ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ + ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ → ${}_{}{}^{47}{}_{}{}^{}\mathrm{V}$ are measured to be (5–10)×${10}^{\mathrm{-}18}$ s using the blocking of evaporation residues in Si 〈100〉 single crystal. Similar measurements using low energy alpha particles evaporated in the decay of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ yield lifetimes in the same range. However, the shape of the blocking pattern for the high energy α particles in the same decay is similar to that for the elastically scattered particles indicating a lifetime shorter than ${10}^{\mathrm{-}18}$ s. These results, along with our earlier measurements in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ and those reported by others, show that the lifetimes for the later stages of the compound nuclear decay are nearly the same for nuclei in the mass range 40–160 and are relatively insensitive to the initial excitation energy.

It is shown that the simple correlation of E($2_1^{+}$) and E($4_1^{+}$) energies can be a sensitive indicator of underlying shell structure and, in particular, that recent suggestions of radically different structure near the neutron drip line may be most easily signaled by this observable.

All the orbital M1 excitations, at both low and high energies, obtained from a rotationally invariant quasiparticle random-phase approximation, represent the fragmented scissors mode. The high-energy M1 strength is almost purely orbital and resides in the region of the isovector giant quadrupole resonance. In heavy deformed nuclei the high-energy scissors model is strongly fragmented between 17 and 25 MeV (with uncertainties arising from the poor knowledge of the isovector potential). The coherent scissors motion is hindered by the fragmentation and B(M1)<0.25${\mathrm{\mu }}_{\mathit{N}}^2$ for single transitions in this region. The (e,e’) cross sections for excitations above 17 MeV are one order of magnitude larger for E2 than for M1 excitations even at backward angles.

Response functions for isoscalar multipole excitations are calculated for a large range of temperatures and analyzed in terms of transport coefficients. The dynamics of the nucleons is treated semiclassically by applying the collisional Landau-Vlasov equation for the interior region, supplemented by the ‘‘effective nuclear surface approximation’’ introduced previously to describe the dynamics of the surface. Collisions are considered in modified relaxation time approximation with a temperature- and frequency-dependent relaxation time. The strength distribution shows a marked transition from the zero sound like behavior at small temperatures to the one corresponding to collision dominated modes. The latter appear at small frequencies and are underdamped. Within our present model the transition occurs at large temperatures of about T≥4 MeV. For the intermediate temperatures the overdamped modes are found as related to the low-lying peaks in the strength function. The results are illustrated by the calculations of the strength function for the quadrupole excitations in the nucleus ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$.

The Lee-Suzuki iteration method is used to include the folded diagrams in the calculation of the two-body effective interaction ${\mathit{v}}_{\mathrm{eff}}^{\mathrm{}\left(2\right)\mathrm{}}$ between two nucleons in a no-core model space. This effective interaction still depends upon the choice of single-particle basis utilized in the shell-model calculation. Using a harmonic-oscillator single-particle basis and the Reid-soft-core NN potential, we find that ${\mathit{v}}_{\mathrm{eff}}^{\mathrm{}\left(2\right)\mathrm{}}$ overbinds ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ in 0, 2, and 4ħΩ model spaces. As the size of the model space increases, the amount of overbinding decreases significantly. This problem of overbinding in small model spaces is due to neglecting effective three- and four-body forces. Contributions of effective many-body forces are suppressed by using the Brueckner-Hartree-Fock single-particle Hamiltonian.

The differences found in the relativistic and nonrelativistic methods used in the literature to account for short range nuclear correlations in the decay of Λ hypernuclei are analyzed. By means of a schematic microscopic model for the origin of correlations, the appropriate method to include them in nuclear processes is derived and is found to be the same one used in the nonrelativistic approach. The differences do not stem from relativistic effects but from the improper implementation of the correlations in the relativistic approach, which leads to several pathologies as shown in the paper. General formulas are given to evaluate the nonmesonic decay width of finite hypernuclei and results are obtained for ${}_{\mathrm{\Lambda }}{}^5{}_{}{}^{}\mathrm{He}$ and ${}_{\mathrm{\Lambda }}{}^{12}{}_{}{}^{}\mathrm{C}$.

We explore the possibility that a stable nucleus has halolike structure in high isospin excited states. As an example the structure of the 3.563 MeV $0^{+}$ state of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ is studied in a fully microscopic α+p+n three-cluster model, because it is an isobaric analog state of ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ with two-neutron halo structure. An extensive calculation with isospin mixing has shown that the state has spatially extended halolike structure formed by the neutron and the proton outside the α particle. Electron scattering form factors related with the state are reproduced fairly well.

Comparison is made between calculations of transverse electric form factors using the standard expression for the electric multipole operator and those obtained by invoking current conservation in the long wavelength limit and for arbitrary momentum transfer. In all cases, only the free-nucleon one-body current and charge operators are explicitly used. Results are presented for select E2 transitions in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. It is found that the form factors yielded by the various operators differ significantly when the conventional 0ħω shell model wave functions are used, confirming that these do violate conservation of the usual free-nucleon current. For these cases, the data are best reproduced using the operator with current conservation invoked in the long-wavelength limit. However, the variation between results is much smaller when multishell models of nuclear structure are used, all three forms of the operator yielding good agreement with existing data, suggesting that the wave functions obtained from these still practicable models are significantly closer to being current conserving.

Normal bands on the well-deformed odd-A nuclei are studied with the cranking Bohr-Mottelson Hamiltonian proposed by us. The condition of validity of the model and comparison with the Harris expansion are discussed. The phenomena of identical bands are briefly discussed with the help of the present model.

The general collective (or Frankfurt) model (GCM) is applied to the barium isotopes with A=124–132. A good description of the experimental level schemes is obtained and in particular, the staggering effect in the quasi-γ bands of these nuclei is reproduced. The description of the E2 transition strengths is also satisfactory but the deviations observed for specific weak transitions indicate some crudeness in the present quadrupole operator of the model. The comparison of the derived potential energy surfaces (PES) with microscopic nuclear shape calculations shows an overall reasonable agreement. The description of the spectroscopic properties is compared to the results obtained in the framework of other collective models used in the A≊130 mass region. The structure of the GCM wave functions is investigated and correspondences with the quantum numbers of the interacting boson approximation (IBA) wave functions are considered.