We report the measurements on interaction mean free paths of the multiple He fragments produced by the collisions of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ ions at 200 GeV/nucleon in nuclear emission. Within experimental errors, the mean free paths have been found to be independent of the He multiplicity and the size of the target nucleus.

A simple method is proposed for determining the impact parameter in relativistic nucleus-nucleus collisions. Assuming a monotonous correlation between multiplicity and impact parameter, the multiplicity dependence of the measured cross section is interpreted as an impact-parameter dependence of the geometrical reaction cross section. The reliability of this method is checked to be excellent within the framework of the intranuclear cascade model. Its application to data analysis at lower and higher energies is suggested.

We have examined the behavior of the forward-to-backward ratio R of the cross section for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(γ,p)n reaction. The data show a weak dependence of R on the photon energy and group around a value of 1.5 which agrees with the prediction of a simple quark model. An energy dependence of R is predicted in the quark-gluon string model and is shown to be connected to the ratio of d/u quark distributions in the proton.

Sub-Coulomb cross sections for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C→α${+}^{20}$Ne, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C→p${+}^{23}$Na, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C→n ${+}^{23}$Mg are calculated in a semistatistical framework that allows a comparison to experiment in terms of the general energy dependence and magnitude. Intermediate structure previously produced in the generalized doorway model via calculations of the structure factor is not evident in the present approach because of the large energy dependence of the reaction cross sections. The compound nucleus is described in a generalized doorway model where the doorways are obtained by coupling the shape resonances in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C to the single and mutual excitation channels. The transmission coefficients for decay are determined in a modified form of the Hauser-Feshbach method. Agreement is good in terms of energy dependence and magnitude even though the experimental cross sections vary by about 4 orders of magnitude between 3 and 5 MeV c.m.

The temperature dependence of fission barriers has been interpolated from the results of recent theoretical calculations and included in a statistical model code. It is shown that the inclusion of temperature dependence causes significant changes to the values of the statistical model parameters deduced from fits to experimental data.

Significant discrepancies between theory and experiment have previously been noted for nucleon emission via electromagnetic processes in relativistic nucleus-nucleus collisions. The present work investigates the hypothesis that these discrepancies have arisen due to uncertainties about how to deduce the experimental electromagnetic cross section from the total measured cross section. An optical-model calculation of single neutron removal is added to electromagnetic cross sections and compared to the total experimental cross sections. Good agreement is found thereby resolving some of the earlier noted discrepancies. A detailed comparison to the recent work of Benesh, Cook, and Vary is made for both the impact parameter and the nuclear cross section. Good agreement is obtained giving an independent confirmation of the parametrized formulas developed by those authors.

We estimate, to leading order in the nuclear matter density, the effect of antisymmetrizing quarks belonging to different nucleons upon the binding energy per nucleon in nuclear matter. A simple Gaussian model for the nucleon quark wave function, together with a one-gluon-exchange potential between quarks, is assumed. Using a linked cluster expansion developed earlier for nuclear matter, we calculate separately the effect of quark interchanges upon the kinetic, hyperfine, Coulomb, and contact terms in the Hamiltonian. A strong net repulsion is found which grows rapidly with the dimensionless parameter α=${\mathit{r}}_0$${\mathit{k}}_{\mathit{F}}$, where ${\mathit{k}}_{\mathit{F}}$ is the nuclear Fermi momentum and ${\mathit{r}}_0$ the nucleon size.

The absolute differential cross section for the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(p,γ${)}^4$He reaction has been measured at ${\mathrm{\theta }}_{\gamma }$=90° for ${\mathit{E}}_{\mathit{p}}$=2.0–15.0 MeV, corresponding to photon energies ${\mathit{E}}_{\gamma }$=21.3–31.1 MeV. The present results are 35% lower than previously measured (p,γ) cross sections and are in excellent agreement with recent (γ,p) data obtained with monoenergetic photons. Comparing our results to current photoneutron cross sections gives a ratio σ(γ,p)/σ(γ,n)=1.09±0.17 for ${\mathit{E}}_{\gamma }$=24–31 MeV. This ratio is consistent with conventional theoretical predictions, indicating that no charge-symmetry violation in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is required.

Neutron-rich rare-earth isotopes were produced in multinucleon transfer reactions between ${}_{}{}^{170}{}_{}{}^{}\mathrm{Er}$ ions and ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{W}$ targets. On-line mass separation was used together with β- and γ-ray spectroscopy in these studies. At mass A=169, the heaviest known dysprosium isotope, 39(8) s${,}^{169}$Dy, was identified. It was observed to ${\mathrm{\beta }}^{\mathrm{-}}$ decay to the ground state of ${}_{}{}^{169}{}_{}{}^{}\mathrm{Ho}$ or through a level at 1578 keV. In the A=171 mass chain, a partial decay scheme for 55(3)-s ${}_{}{}^{171}{}_{}{}^{}\mathrm{Ho}$ was determined.

Charged-particle-γγ and neutron-γγ coincidences are employed to identify γ-ray transitions in the ${\mathit{T}}_{\mathit{z}}$=1/2 nucleus ${}_{}{}^{67}{}_{}{}^{}\mathrm{As}$, produced in the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{32}$S,αp${)}^{67}$As and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${(}^{33}$S,αpn${)}^{67}$As reactions at bombarding energies between 95 and 110 MeV. Gamma-ray angular distributions, γγ coincidences, and γγ angular correlations are used to deduce a level scheme for ${}_{}{}^{67}{}_{}{}^{}\mathrm{As}$ up to 5.7 MeV.

Excitation-energy spectra resulting from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(γ,p) reactions at 90° have been measured with tagged photons of about 61 and 77 MeV. Decay to several discrete states is discussed. Evidence is shown for an absorption process where the photon interacts with a T=1 proton-neutron pair, instead of the T=0 p-n pair implicit in the quasideuteron model.

Excited states of ${}_{}{}^{151}{}_{}{}^{}\mathrm{Pm}$ have been observed using the ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$(α,p2n) reaction at a beam energy of 35 MeV. Levels with spin up to 19/2 have been seen in a positive parity band built on the 5/$2^{+}$ ground state, and up to 21/2 in a negative parity band built on the 5/$2^{\mathrm{-}}$ level at 117 keV excitation energy. Levels of the same spin but opposite parity are nearly degenerate and there are strong (∼1.1×${10}^{\mathrm{-}3}$ W.u.) electric dipole transitions between members of the two bands. The energy staggering of levels and their electromagnetic decay properties are somewhat different for the two bands.

Pre-scission ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{197}$Au reactions are measured in coincidence with fission fragments in the compound nucleus excitation energy of 48 to 99 MeV. Observed coincident energy spectra of ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are shifted towards lower energies compared to statistical model calculations. The data are analyzed in terms of the spin-dependent level density and emission barriers for the charged particles. The analysis shows that the effect of the spin-dependent level density on the energy spectrum is small and the effective emission barriers for particle emissions are reduced by 1.0±0.4 MeV for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and 1.8±0.4 MeV for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ relative to the corresponding fusion barriers calculated by using optical potentials.

The first experimental results are reported on excited states in the N=Z nuclei ${}_{}{}^{68}{}_{}{}^{}\mathrm{Se}$ and ${}_{}{}^{76}{}_{}{}^{}\mathrm{Sr}$. These data, combined with recent results on germanium, krypton, and zirconium show the importance of deformed shell gaps in stabilizing nuclear shapes in this region, initially polarizing towards oblate then towards prolate shapes with increasing mass. The results present direct tests of a variety of nuclear models, and a clearer picture of the structure of the region now emerges.

A new one-boson-exchange potential is presented in which the pion-nucleon form factor is taken to be much softer than usual. The fit to N-N phase shifts and deuteron properties is quantitatively as good as for recent potentials of more conventional form, such as a former version of the Bonn potential. As anticipated in earlier work the tensor combination of P-wave phase shifts, ${\mathrm{\Delta }}_{\mathit{T}}$, is somewhat reduced for the new potential in comparison with the original.

Elastic-scattering angular distributions are presented for the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${+}^{48}$Ca system at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=59.5 and 63.1 MeV. Qualitative agreement is observed at both energies with a coupled-channels calculation that includes inelastic-scattering and single-nucleon transfer channels, together with an additional positive Q-value channel with coupling strength adjusted to fit the sub-barrier fusion yield.

We reexamine the well-known problem of isospin forbidden E1 decays in self-conjugate nuclei in the light of a recent claim suggesting that the E1 decay in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ violates Siegert’s theorem. We first discuss the importance of including, through isospin mixing, giant dipole and monopole components if agreement with observed lifetimes has to be achieved. We then show that the same microscopic calculation which yields broad agreement with (e,e’) and lifetimes results in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ also asserts the validity of Siegert’s theorem. We conclude by suggesting that the claim regarding a violation of Siegert’s theorem can only be definitely ascertained once additional data at low momentum transfer become available.

The strong interaction shifts and widths of the antiproton-deuteron atom are calculated within a simple three-body model. The nuclear p¯-d optical potential is obtained from a projected form of the Faddeev equations with rank one, separable, S-wave two-body potentials. The N-N¯ potential parameters are fit to the zero-energy scattering results of the Graz potential. The Coulomb potential is combined with the nuclear optical potential to obtain the atomic levels from the Schrödinger equation. The truncation of the Faddeev model optical potential to the level of the standard tρ impulse approximation overestimates the shifts and widths by up to 10% and 30%, respectively. The use of first-order perturbation theory for the atomic eigenvalue overestimates the widths by one order of magnitude.