Conversion processes in light nuclei with transition energies above the ${\mathrm{e}}^{+}$, ${\mathrm{e}}^{\mathrm{-}}$ pair creation threshold are investigated within an analytical framework. In particular, we evaluate the ratio of electron transition probabilities from the negative energy continuum into the atomic K shell and into the positive energy continuum, respectively. The possible role of monoenergetic positron conversion with respect to the striking peak structures observed in ${\mathrm{e}}^{+}$ spectra from very heavy collision systems is examined.

The phenomenological prediction of properties of nuclei far off stability is greatly simplified in the $N_{\mathrm{p}{N}_{\mathrm{n}}}$ scheme for three reasons: the systematics for each observable is smooth, the similarity of different regions provides a paradigm for unknown cases and, primarily, the $N_{\mathrm{p}{N}_{\mathrm{n}}}$ scheme often transforms the process of extrapolation into one of interpolation. The same ideas find expression in the concept of $N_{\mathrm{p}{N}_{\mathrm{n}}}$ multiplets that can link known and unknown nuclei.

Theoretical results on the asymmetry function and angular distribution parameters for deuteron photodisintegration are obtained by adding the one- and two-body relativistic corrections to the charge density and meson exchange corrections to the current density to the normal E1, M1, and E2 multipoles and compared with the recent measurements of De Pascale et al. Phenomenologically, it is found that agreement with the angular distribution coefficients which depend on the E2 transitions can be improved if the E2 radial matrix elements are reduced by about 15%. The physical process responsible for this reduction is not clear.

The effects of giant resonance couplings on the elastic scattering of nucleons from light, spherical nuclei are examined over a wide range of incident energies (18–46 MeV). General trends in the large-angle elastic scattering data for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ that are poorly described with the conventional optical model are qualitatively reproduced with an uncomplicated picture for the giant states. Comparison is made between this approach and earlier calculations involving giant resonances and l-dependent potentials.

Recent data on the photodistintegration of the deuteron in energy range 10 to 625 MeV have been fit to a simple phenomenological function. The result provides a representation of the cross section which should be useful for interpolating between measured points or for providing simple input for calculations such as impulse approximation calculations of (p,γ) reactions.

The nuclear matter parameters and the single-particle properties are compared for the standard (non-) local Paris potential and its separable representation, given by the Graz group. The results are discussed.

The analyzing power for the scattering of polarized protons via a compound-nucleus resonance contains ‘‘irregular’’ (parity violating) terms if, as a consequence of weak nucleon-nucleon forces, some amount of parity mixing takes place in the resonant state. In this comment, the case of transverse polarization is discussed, and the parity violating effect–corresponding to an up-down asymmetry of the angular distribution with respect to the polarization direction–is deduced from the irregular (and regular) transition amplitudes.

Experimental considerations usually favor measurements of the longitudinal rather than the irregular transverse analyzing power. This is particularly true for the case of the parity mixing in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$. Some typographical errors in our published expressions are corrected.

The occurence of a coexisting four-particle, four-hole band built on the first excited $0^{+}$ state in the doubly closed subshell nucleus ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$ is established from (n,n’γ) reaction experiments and previous multiparticle transfer studies.

Cross sections have been measured for ${\pi }^{+}$ and ${\pi }^{\mathrm{-}}$ scattering to the giant resonance region of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ with 162-MeV pions. The value of R=σ(${\pi }^{\mathrm{-}}$)/σ(${\pi }^{+}$) measured for the giant quadrupole resonance is 2.72. A distorted wave impulse approximation analysis of these data using collective model form factors gives the ratio of neutron to proton matrix elements to be 3.8. This is much larger than expected from the hydrodynamical model which predicts a value of N/Z of 1.54.

The reaction ${}_{}{}^{20}{}_{}{}^{}$Ne${+\mathrm{}}^{54}$Fe at beam energies of 216 and 294 MeV has been used to study the breakup of Ne by measuring the correlations between fast α particles and quasi-elastic projectile-like fragments. The experimental data can be described by sequential decay even for high excitation energies in the primary fragment, where the half-life of the states is comparable to the nuclear reaction time.

The level scheme of ${}_{}{}^{219}{}_{}{}^{}\mathrm{Ra}$ established via a study of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$${(}^{14}$C,3n${)}^{219}$Ra reaction is presented. The structure of the rotational band based on the ground state is interpreted as reflecting a $g_{9/2}$ valence neutron weakly coupled to a spherical ${}_{}{}^{218}{}_{}{}^{}\mathrm{Ra}$ core. A non-yrast side band is observed, having tentative ${\mathrm{}(11/2)\mathrm{}}^{\mathrm{-}}$, ${\mathrm{}(15/2)\mathrm{}}^{\mathrm{-}}$, . . . level assignments. An ${\mathrm{}(11/2)\mathrm{}}^{\mathrm{-}}$ state could result from the anomalous J=j-2 intermediate strength coupling of a $j_{15/2}$ neutron to the ${}_{}{}^{218}{}_{}{}^{}\mathrm{Ra}$ core. The relevance of a weak coupling model to the understanding of high spin (J>j) parity doublets and the surprisingly different experimentally observed level schemes of ${}_{{\mathrm{}}^2{\mathrm{}}_{88}^{19}}{}^{}{}_{}{}^{}\mathrm{Ra}$ and ${}_{{\mathrm{}}^2{\mathrm{}}_{89}^{19}}{}^{}{}_{}{}^{}\mathrm{Ac}$ are discussed.

Differential cross sections σ(theta) and analyzing powers $A_y$(theta) for neutron scattering to the ground and first $3^{\mathrm{-}}$ excited state of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ have been measured in the energy range from 11 to 17 MeV. Elastic and inelastic scattering measurements have been obtained for $A_y$(theta) at energies of 11.0, 13.9, and 16.9 MeV, the inelastic scattering data representing the first (n,n’) measurements of $A_y$(theta) for this nucleus. Differential cross sections for (n,n) and (n,n’) have been obtained at 13.9 and 16.9 MeV. Both the σ(theta) and $A_y$(theta) data at 13.9 MeV have been compared with previous measurements at this energy and the agreement is good, typically within less than 3%. These results have been combined with other σ(theta) and $A_y$(theta) data and total cross section ${\sigma }_T$ measurements to form a large set of scattering and reaction data for incident energies up to 80 MeV. This data set, along with σ(theta) and $A_y$(theta) measurements available for proton scattering in this energy range, has been described in the framework of the coupled-channel formalism. This highly constrained analysis has led to a precise determination of geometries, energy dependencies, and deformation parameters. Further analyses, which dealt with simultaneous couplings to low- and high-energy excited states, have led to improved descriptions of the elastic scattering measurements for σ(theta) and $A_y$(theta) at backward angles. These results confirm that real and virtual excitations of giant resonances cannot be ignored in the description of the reaction mechanism. In this context, it has also been found that corrections to the real central potentials, as estimated by Mahaux and Ngo^ from dispersion relations, help to further improve the fits to elastic scattering observables.

A nuclear structure study of ${}_{}{}^{151}{}_{}{}^{}\mathrm{Sm}$ is presented on the basis of low-energy γ-ray and conversion electron spectroscopy, in connection with thermal neutron capture, and high-energy primary γ-ray measurements following average resonance neutron capture. The level scheme is established up to 1020 keV and incorporates 44 levels. Unique spin and parity assignments are made for 34 levels, and narrow limits are set for the remaining levels. Further possible levels are given between 355 and 1220 keV. Theoretical calculations are presented in the framework of the quasiparticle-rotor model, introducing Coriolis coupling and ΔN=2 interaction. Comparisons between theoretical and experimental results are made for level energies, branching ratios, and multipole mixing ratios.

A recently proposed method for the direct calculation of the S matrix is tested on proton-proton scattering. The agreement with the S matrix calculated from a standard approach is satisfactory. Optimal conditions of the method are thoroughly investigated. Special attention is paid to criteria on the efficiency of the numerical approximation for a limited number of expansion functions. Two criteria are proposed which are based on exact relations in scattering theory: the intertwining property of the wave operators and the commutation property of the S matrix and the free Hamiltonian. As a result of this study we are able to give recommendations for a successful application of the method.

A precise measurement of the polarization-analyzing power difference in p-p elastic scattering has been made at 198.5 MeV to improve the experimental limits on time reversal violation in proton-proton scattering in this energy region. The experiment was performed in a kinematic regime where sensitivities to time reversal violating amplitudes should be high. Experimental methods which eliminated the need to refer to absolute values of the beam polarization or to the analyzing power of a polarimeter were used. The result is (P-A)=0.0047 with a statistical uncertainty of ±0.0025 and a systematic uncertainty of ±0.0015.

The reaction d+p→p+p+n is investigated at $E_{\mathrm{lab}{}^{\mathrm{d}=7.4\mathrm{}}}$ MeV. Calculations of the cross section are compared with recent kinematically complete measurements. The Coulomb potential is taken fully into account in the calculations based on the strong approximation of Mo/ller wave operator approach.

The specific distortion effect of the three-nucleon cluster in the n+t or p${+\mathrm{}}^3$He system is studied by using the pseudostate method in the resonating-group formulation. The result indicates that such an effect is significant mainly at low energies around the broad resonance in the Pauli-favored l=1 state. In the higher-energy region, a comparison between differential cross sections calculated with and without distortion shows that this effect has only a minor influence.

An alternative formulation of the post form of the distorted wave Born approximation for the breakup of light ions is proposed, which results in well-behaved integrals and eliminates the need for a zero-range approximation for simplification. It also emphasizes the underlying unity of the prevailing theories of breakup in limiting cases.