We have calculated the total Gamow-Teller strength $S_{\pm }$ in the even-even sd-shell nuclei making use of the sum rule technique. The ground state wave function is obtained from the shell model calculation in the full (sd${)}^n$ space. It is shown that the proton-neutron correlation effect causes a considerable amount of reduction of the total Gamow-Teller strength. It is also shown that the reduction of the isospin component in $S_{\mathrm{-}}$ induced by the configuration mixing becomes more significant with increasing isospin.

We show that the criticism of the work of Thies and of Cooper and Jennings is based on a misunderstanding of the relation between the relativistic and nonrelativistic models, as well as the relation between coordinate space and momentum space calculations. The presence of structure in the particle-only propagator is shown by direct calculation.

At issue is the identification of the physical mechanism that causes the distinction between the nucleon-nucleus scattering observables predicted by Dirac and Schrödinger implementations of the impulse approximation for the optical potential. We clarify the decisive role of an early variant of the Dirac approach in addressing this issue. Using this basis, recent conjectures concerning the physical mechanism are easily seen to be misleading. The elimination of apparent formal mathematical difficulties at high momenta, which arise from the noncompactness of local form factors, is also straightforward within this approach using well-known techniques in scattering theory.

Analyzing powers have been measured for the reaction ${}_{}{}^2{}_{}{}^{}$H(p→,γ${)}^3$He at a proton beam energy of 800 MeV. The results are in good agreement with microscopic calculations. At this energy the data are most sensitive to the meson-exchange amplitudes. Proton initial-state interactions also play an important role.

The angular distribution for elastic scattering of 179.3 MeV antiprotons by deuterium has been measured. The data should provide further constraints on the elementary p-n amplitudes.

Cross sections have been measured for the excitation of the 12.71 MeV, T=0, and 15.11 MeV, T=1, $1^{+}$ states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ by 50 MeV ${\pi }^{\pm }$ scattering. The cross section ratio, R=σ(12.7 MeV)/σ(15.1 MeV), was found to be 7.5±1.5 for ${\pi }^{+}$ and 6.6±1.5 for ${\pi }^{\mathrm{-}}$ at 50 MeV, giving an isospin averaged value of R=7.05±1.06. These results indicate that the anomalous behavior of R is attributable to the energy dependence of the T=1 $1^{+}$ level. The data also indicate that the impulse approximation is probably invalid at 50 MeV, contrary to the conclusions of a recent study at 65 MeV.

Measurements of spin-flip probabilities for inelastic scattering of 318 MeV protons from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ reveal that much of the background underlying the giant dipole and quadrupole resonances at small angles is from ΔS=1 transitions. This holds the promise of allowing a much better estimate of this background than has previously been possible; one model-dependent parameter is necessary. Subsequent analysis with a first estimate of this parameter is presented.

The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(γ,p${)}^{11}$B reaction has been studied using tagged photons and a new type of detector system that allowed proton groups leading to ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ excited states to be resolved for the first time. A comparison between the intensities of states excited in the (γ,p) and (e,e’p) reactions reveals large differences, in particular for the 6.8 MeV doublet of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$. This may indicate the importance of two-nucleon effects for the (γ,p) reaction which contrasts the single nucleon virtual photon absorption observed for (e,e’p) reactions.

New determinations of the D-state amplitudes for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and the triton have been made by studying the tensor analyzing powers for the ground state transitions in ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$(d→${,}^3$He${)}^{30}$Si and ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$(d→,t${)}^{30}$P reactions at $E_{\mathrm{d}\mathrm{\simeq }16}$ MeV. Exact finite range distorted-wave Born approximation analyses of these data for an angular range of 20° to 135° yields $D_2$${(}^3$He)=-0.24±0.04 ${\mathrm{fm}}^2$ and $D_2$(t)=-0.25±0.05 ${\mathrm{fm}}^2$. The asymptotic D/S-state ratios, η, are also determined and compared with predictions of Gibson-Lehman wave functions for the three-nucleon system. We obtain η${(}^3$He)=-0.042±0.007 and η(t)=-0.050±0.010. .AE

As an alternative to conventional meson-exchange models, we study exclusive p¯p→Y¯Y production in the nonrelativistic one-gluon-exchange and the ${}_{}{}^3{}_{}{}^{}\mathrm{P}_{\mathrm{o}}^{}{}_{}{}^{}$ model. Adjusting the overall coupling strengths at $P_{\mathrm{lab}=2.0\mathrm{}}$ GeV/c, the main uncertainty originates from the oscillator constant. Though both models yield qualitative agreement with experiment, a more detailed comparison favors the one-gluon-exchange model.

The total ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$(n,p${)}^7$Li cross section has been measured from 25 meV to 13.5 keV. These energies correspond to temperatures of T=2.9×${10}^{\mathrm{-}7}$ to 0.16 GK. For thermal neutrons the cross sections to the ground state ($p_0$) and the first excited state (${\mathit{p}}_1$) of ${}_{}{}^7{}_{}{}^{}\mathrm{BLi}$ are 38 400±800 b and 420±120 b, respectively. This result for the total ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$(n,p${)}^7$Li thermal cross section is about 25% lower, and is approximately a factor of 10 more precise than previous published measurements. For energies above 100 eV, a significant departure from a 1/v shape for the total cross section is observed. The data were analyzed using a single-level approximation, and were also analyzed together with other data using multilevel-multichannel R-matrix theory. Results are presented for the properties of the $2^{\mathrm{-}}$ threshold state and for a possible nearby $2^{\mathrm{-}}$ state. The astrophysical reaction rate, $N_A$〈σv〉, was calculated from the measured cross sections for the combined $p_0$ and $p_1$ transitions. The resulting reaction rate is approximately 60–80 % of the rate currently in use. This reduction in the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$(n,p${)}^7$Li reaction rate could result in a calculated increase in the production of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ during the big bang by as much as 20%.

Coulomb effects are relevant near the breakup threshold and simple corrections of neutral Faddeev calculations are not sufficient. At a center-of-mass energy $E_{\mathrm{c}.\mathrm{m}.\mathrm{}=0.243\mathrm{}}$ MeV, an approximate Coulomb Faddeev calculation is shown to be reliable. Comparison to experimental data shows deviations, which remain unexplained in terms of pure two-body nuclear-plus-Coulomb forces.

The off-shell properties of two-nucleon t matrices are studied for both uncoupled and coupled channels. Complex t matrices have been obtained using both matrix inversion and continued fraction techniques of solution and predicated upon a standard phenomenological form (Reid), a meson exchange model (Paris), and a new phenomenological form that we have developed, of the two-nucleon interaction. The off-shell t matrices from these interactions are very similar whenever they give essentially the same phase shifts at all energies. When they do not, the associated off-shell t matrices diverge so substantially that any data depending upon these off-shell t matrices will differentiate between the interactions.

From a comparison of experimental results with various theoretical calculations of N-N spin transfer parameters in N-d scattering, we find a very strong correlation between the N-d doublet scattering length and these spin transfer parameters, in view of which, it is extremely unlikely that useful information about the N-N interaction can be obtained from these parameters which is not already implicit in the value of the N-d doublet scattering length. In addition, these spin parameters carry some information about the noncentral part of the N-N interaction, which can be conveniently found and studied through the consideration of a new function ΔK of these spin parameters.

The structure of ${}_{}{}^{99}{}_{}{}^{}\mathrm{Mo}$ has been investigated via the ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$(α,n) reaction at bombarding energies between 10 and 18 MeV. Excitation functions and angular distributions of deexcitation γ rays have been measured to provide information on the spins of levels deduced in γ-γ coincidence measurements carried out at 13 and 16 MeV. Several new medium-spin levels have been evinced from the present measurements and give a clear indication that collective features play an important role in defining the nuclear structure of ${}_{}{}^{99}{}_{}{}^{}\mathrm{Mo}$ which can be considered as a typical transitional nucleus in the region around A=100.

The energy spectra of neutrons emitted from 14.1-MeV-neutron-induced reactions on Ag, Cd, In, Sn, Sb, and Te were measured at 70° in order to investigate the shell and odd-even effects in the preequilibrium (n,n’) process. The cross sections integrated over the outgoing energies of 7–10 MeV, where the preequilibrium process is dominant, increased monotonically with increasing atomic numbers of all scatterers except Te. The results of calculations based on the exciton model showed an underestimation in 7–10 MeV only for Te. This underestimation could be explained by taking into account the contribution from the collective excitations of the low energy octupole resonance by the direct process. As a result, it was found that there were no appreciable shell and odd-even effects in the preequilibrium (n,n’) process that leaves the residual nucleus into the continuum region.

Energy spectra of projectile-like fragments from collisions of 35 MeV/nucleon ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ with ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ are presented for laboratory angles of 10° and 30°. At 10° each spectrum shows a pronounced quasielastic peak at E/A just below 35 MeV. The peak widths are compared with predictions of the fragmentation model of Goldhaber and the peripheral model of Friedman. At 30° each spectrum is a decreasing exponential with slope dependent on the mass of the fragment. Coalescence-model calculations are compared with these data. Relative isotope distributions are presented for both angles.

Angular momentum features are introduced into a formalism, previously proposed, for calculating the statistical emission of complex nuclear fragments. The formalism follows the evolution of an excited system as it deexcites by emitting particles which carry away mass, charge, energy, and angular momentum from the residue. Instantaneous differential emission rates are developed using detailed balance and including the effects of the angular momentum of the residue and the emitted fragment. The rates are used to calculate features of the deexcitation process. Illustrative examples of calculated results are provided for the instantaneous values of various properties of the residue which obtain during the evolution of the system. Results of calculations for final multiplicities, spectra, and angular distributions are also provided. The examples emphasize the influence of angular momentum.

The odd-proton nucleus ${}_{}{}^{133}{}_{}{}^{}\mathrm{Pr}$ has been investigated using the ${}_{}{}^{118}{}_{}{}^{}\mathrm{F}$,4n) and ${}_{}{}^{117}{}_{}{}^{}\mathrm{F}$,3n) reactions. Several rotational bands could be followed up to high spins. The yrast band, built on a decoupled $h_{11/2}$ proton, shows an upbend at ħω=0.43 MeV when two additional $h_{11/2}$ protons align. Two positive-parity side bands of opposite signature were established, both showing a band crossing at ħω=0.27 MeV with a gain in alignment Δ$i_x$∼8ħ when two $h_{11/2}$ protons align. This low crossing frequency, compared to that observed in the ${}_{}{}^{132}{}_{}{}^{}\mathrm{Ce}$ core nucleus, is partly explained by a reduction in the proton pairing gap. Three ΔI=1 bands were observed; the lowest one is believed to represent a collective rotation of an oblate shape. The shape change is induced by the alignment of a pair of $h_{11/2}$ neutrons from the upper midshell driving the nucleus from a prolate to an oblate shape.