The orbiting cluster model is applied to the basic presently available data on resonances in heavy-ion-induced reactions. The model is shown to correctly predict the presence of resonances and give a good overall agreement with the measured resonance energies.

Allowed ${\mathrm{\beta }}^{+}$-decay branches of very proton-rich sd-shell nuclei up to the proton drip line are calculated by the complete sd-space shell model. The ${\mathrm{\beta }}^{+}$-decay half-lives calculated with the global quenching factor (${\mathit{g}}_{\mathit{A}}^{\mathrm{eff}}$/${\mathit{g}}_{\mathit{A}}$${)}^2$=0.60 are in reasonable agreement with existing experimental data. However, considerable deviations of the quenching factor from the global value are obtained in a comparison of the theoretical and experimental ft values in the large-Q-value window. Probable candidates for the β-delayed two-proton emission are suggested with the predicted ${\mathrm{\beta }}^{+}$-decay branching strengths to states above the proton-emission threshold energy.

Intermediate mass fragments emission in intermediate-energy nucleus-nucleus collisions has been studied in the framework of a generalized model where the fragments are assumed to be emitted from binary fissionlike decay of the fully equilibrated compound nucleus. The present formulation, with a schematic exit channel shape configuration and simple rotating liquid-drop nuclear potential, has been found to explain most of the intermediate mass fragments emission cross sections reasonably well without incorporating any free parameters in the calculation.

Pion absorption by ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ was studied at ${\mathit{T}}_{\mathrm{\pi }}$=165 MeV in a kinematically complete experiment. The cross section for absorption on a (pn) pair of nucleons, ${\mathrm{\sigma }}_{\mathit{p}\mathit{n}}$(${\mathrm{\pi }}^{+}$), was found to be 17.0±2.6 mb; that for absorption on a (pp) pair, ${\mathrm{\sigma }}_{\mathit{p}\mathit{p}}$(${\mathrm{\pi }}^{\mathrm{-}}$), 0.91±0.20 mb. The angular distribution in the πNN center-of-mass system for ${\mathrm{\sigma }}_{\mathit{p}\mathit{n}}$(${\mathrm{\pi }}^{+}$) resembles that for the ${\mathrm{\pi }}^{+}$+d→p+p reaction while the angular distribution for ${\mathrm{\sigma }}_{\mathit{p}\mathit{p}}$(${\mathrm{\pi }}^{\mathrm{-}}$) is strongly backward peaked. Evidence that a significant fraction of the absorptions involves all three target nucleons is seen in the angular correlation between the two detected nucleons as well as in the momentum distribution of the unobserved nucleon. For ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ absorption, the three-body cross sections were found to be 9.6±2.1 and 4.2±01.2 mb, respectively. Neither initial- nor final-state interactions appear to be major contributors to the observed three-body absorption, though initial-state interactions may be contributing to the enhancement of the three-body ${\mathrm{\pi }}^{+}$ absorption at the Δ resonance.

In order to search for isospin-2 dibaryons and to study the inelastic nucleon-nucleon channels producing at least two pions, the differential cross sections and analyzing powers have been measured for the p(p→,${\mathrm{\pi }}^{\mathrm{-}}$)X reaction with polarized proton beams of 1.45, 2.1, and 2.7 GeV. The pions were detected at an angle of 13.8° by the SPESIII spectrometer located at Laboratoire National Saturne. No statistically significant evidence for structures corresponding to πNN bound states or six-quark states could be established. However, upper limits to the cross section for such processes are deduced. The data analysis in terms of phase space has shown that as the bombarding energy increases, ${\mathit{N}}^{\mathrm{*}}$N final states have to be taken into account besides the usual NΔ and ΔΔ processes in order to adequately describe our results.

The ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,γ${)}^4$He reaction is studied at center-of-mass energies below 500 keV, where it is dominated by the E2 transition from the ${}_{}{}^5{}_{}{}^{}$${\mathit{S}}_2$ continuum state to the ground state of the α particle. Both the ${}_{}{}^5{}_{}{}^{}$${\mathit{S}}_2$ continuum and the ground states are calculated with the variational Monte Carlo method using the realistic Argonne-${\mathit{v}}_{14}$ two-nucleon and Urbana model-VII three-nucleon interactions. A qualitative agreement with the observed cross section is obtained. This reaction can proceed only through the D states in the deuteron and/or in the α particle. It is found that, depending upon the continuum wave function, the contributions of the deuteron and α-particle D states can either add to produce a large cross section, or cancel. The reaction is thus very sensitive to the continuum wave function.

The dynamical treatment of the nonrelativistic three-body problem with Coulomb and short-range interactions is reexamined. The screening technique is abandoned in favor of the general two-potential formalism and a set of well-behaved three-body equations is derived. An approximate Alt-Grassberger-Sandhas-type form of the new equations is also proposed that treats the long-range polarizability forces to first order and preserves post-prior symmetry.

High spin states in ${}_{}{}^{74}{}_{}{}^{}\mathrm{Kr}$ were investigated in the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{40}$Ca,α,2p${)}^{74}$Kr at 125 and 140 MeV. A new decay scheme was established up to probable spin I=20. The rotational structure was found to be similar to ${}_{}{}^{76}{}_{}{}^{}\mathrm{Kr}$, showing a double alignment in the ground-state band and sidebands with constant moments of inertia. Measured lifetimes using the Doppler-shift attenuation method indicate very collective E2 transitions in the ground-state band.

Data are presented which indicate the existence of F-spin multiplets for the shape-coexistent intruder states of sequences of nuclei differing by an α particle. We argue that these intruder F-spin multiplets, or, equivalently, F-spin analog states, occur because of their larger and more nearly equal values of ${\mathit{N}}_{\mathrm{\pi }}$${\mathit{N}}_{\nu }$.

We present a special two-energy-two-angle amplitude which can be rigorously derived for the pion-proton bremsstrahlung (${\mathrm{\pi }}^{+}$pγ) process near the ${\mathrm{\Delta }}^{++}$(1232) resonance and report the magnetic dipole moment of the ${\mathrm{\Delta }}^{++}$,${\mathrm{\mu }}_{\mathrm{\Delta }}$, extracted from existing data. The extracted value of ${\mathrm{\mu }}_{\mathrm{\Delta }}$ are 3.7–4.2 e/2${\mathit{m}}_{\mathit{p}}$ from one set of data and 4.6–4.9 e/2${\mathit{m}}_{\mathit{p}}$ from another. Here, ${\mathit{m}}_{\mathit{p}}$ is the proton mass. The overall agreement between the theortical predictions calculated with the extracted ${\mathrm{\mu }}_{\mathrm{\Delta }}$ and the experimental measurements is excellent.

Pion production in relativistic heavy-ion collisions is examined with the use of the unitarity relation. We show that the density of states for pion production in an absorptive nuclear medium is not inversely proportional to the in-medium pion group velocity; it depends equally on the imaginary part of the pion self-energy.

We show that, from the experimentally measured differential cross section for two-particle emission in peripheral collisions, it is possible to estimate an average correlation length inside nuclear matter.

Hartree-Fock calculations are performed for deformed nuclei ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ in the relativistic quantum-field-theory framework, the exchange of σ, ω, ρ, and π mesons and photons are included, the coupling constants are adopted from relativistic Hartree-Fock nuclear-matter calculation. Compared to the Hartree results, binding energies are improved by around 8%; however, no appreciable improvement on the quadrupole moments is observed.

The physics of high-spin states in nuclei in terms of broken pairs is discussed. Results of a calculation of the spectrum of the transitional nucleus ${}_{}{}^{194}{}_{}{}^{}\mathrm{Hg}$ including one and two broken pairs are presented. Contrary to cranked single-particle models, broken pair calculations can be compared directly with experiments and thus provide a natural framework to analyze experimental data.

In heavy deformed even-even nuclei the orbital M1 strength below 4 MeV excitation, the so-called ‘‘scissors mode,’’ shows a striking correlation with the E2 strength to the first excited $2^{+}$ states. A saturation effect, common to both E2 and M1 transitions, is observed before midshell. The correlation and the saturation effect are discussed.

The systematics of energy ratios of successive levels of collective bands in medium- and heavy-mass even-even nuclei are studied. A measure of their deviation from the vibrational and rotational limiting values is found to have different magnitude and angular momentum dependence in the vibrational, γ-unstable and rotational regions. The usefulness of this new criterion for distinguishing between different kinds of collective behavior is demonstrated in the case of intruder and octupole bands.

The d+d and p+t partial and total reaction cross sections are computed with a multiconfiguration resonating-group method. The model space employed is spanned by p+t, n+h, d+d, and pseudoinelastic configurations involving deuteron pseudoexcited states. The results show that, at energies where the influence of relatively sharp resonance levels is small, the calculated cross sections for the reactions d(d,p)t, d(d,n)h, and p(t,n)h agree well with experiment. On the other hand, it is also found that, for d+d going into three- and four-particle channels, the calculated reaction cross sections are much too small, suggesting that the inclusion of direct-breakup processes alone through the use of deuteron pseudoinelastic configurations is not sufficient. Because of this, we conclude that the model space employed here is still not extensive enough, especially in the channel spin S=2 state, and should be further expanded to include cluster-rearrangement configurations p+${\mathit{t}}^{\mathrm{*}}$ and n+${\mathit{h}}^{\mathrm{*}}$, where ${\mathit{t}}^{\mathrm{*}}$ and ${\mathit{h}}^{\mathrm{*}}$ represent excited states of the three-nucleon systems having n+d and p+d cluster structures with relative orbital angular momentum I=1 and spin angular momentum S=3/2.

Recent experimental results on nucleon-antinucleon annihilation reactions of the type N¯N→πX have provided evidence for a new mesonic state ${\mathit{X}}_2$ with quantum numbers ${\mathit{J}}^{\mathrm{\pi }\mathit{C}}$(${\mathit{I}}^{\mathit{G}}$)=$2^{++}$($0^{+}$) which lies outside of the usual quark-antiquark (QQ¯) tensor meson nonet of flavor SU(3). We show that the observed production rates of ${\mathit{X}}_2$ from atomic p¯p states of orbital angular momentum L=0,1, as well as the decay characteristics of ${\mathit{X}}_2$, namely, its preference for ρρ over ππ decay and the absence of an observable K¯K mode, are consistent with an interpretation of ${\mathit{X}}_2$ as a quasinuclear bound state of the N¯N potential. The principal binding mechanism for such states is provided by the coherent tensor forces for isospin I=0 which arise from meson exchanges. We review the evidence for the $0^{++}$($0^{+}$) and $1^{\mathrm{-}\mathrm{-}}$($0^{\mathrm{-}}$) states predicted in this model and apply the ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_0$ strong-coupling quark model to estimate the decay branching ratios for a variety of N¯N bound states. Key experimental tests of our interpretation are discussed.

Energetic photon production in proton-neutron as well as in proton-proton collisions at intermediate bombarding energies are investigated in a meson-exchange potential model calculation in an effort to provide a more reliable basis for calculations of hard photon production in heavy-ion collisions. Special attention is paid to the role of the one-body rescattering contribution, which has been neglected in previous work. It is shown that this contribution enhances the cross section for photon energies only near the maximum value allowed kinematically. As a function of photon energy, both pn and pp bremsstrahlung inclusive cross sections are shown to be rather flat except in the low photon energy region. The shape of the angular distribution is, to a large extent, determined by the convection current contribution, which in the soft-photon limit has a well-known dipole shape in the case of pn bremsstrahlung and a quadrupole shape in the case of pp bremsstrahlung. For photon energies above ∼150 MeV where the magnetic current contribution dominates over the convection contribution, the shape of the angular distribution is roughly of a ${\cos }^2$θ form. The internal current gives rise to a nearly isotropic angular distribution. The ppγ cross section is shown to be very small compared to the pnγ cross section, even for considerably high-energy photons, because of the two-body current contribution, which is mostly absent in pp bremsstrahlung. The present calculation yields np bremsstrahlung cross sections which still tend to underpredict the data, although the measurements have large uncertainties.