Double ionization of the atomic K shell accompanying K-shell internal conversion of the 0.662-MeV transition of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Ba}_{}^{\mathrm{m}}{}_{}{}^{}$ has been studied by recording coincidences between Kα hypersatellite x rays and Kα satellite x rays emitted when the double vacancies are filled. The probability per K-shell internal conversion that a double vacancy is formed, $P_{\mathrm{KK}}$(IC), was found to be (10.0±0.9)×${10}^{\mathrm{-}5}$ which is in general agreement with less precise earlier experiments, but is a factor of 2.7±0.3 larger than the relativistic, one-step theory of Mukoyama and Shimizu.

The ${\beta }^{\mathrm{-}}$ decay of 22 h ${}_{}{}^{43}{}_{}{}^{}\mathrm{K}$ ($J^{\pi }$${=(3/2\mathrm{}}^{+}$) was reexamined with the main motive of determining the first-forbidden ${\beta }^{\mathrm{-}}$ branches to the ${(3/2\mathrm{}}^{\mathrm{-}}$ and ${(5/2\mathrm{}}^{\mathrm{-}}$ states more accurately. The branch to the ${(5/2\mathrm{}}^{\mathrm{-}}$ state at 373 keV was established as 0.9(6)% as opposed to a previous limit of <3%. Other ${\beta }^{\mathrm{-}}$ and γ branching ratios and γ-ray energies were determined with considerably improved accuracy. Shell-model calculations in full (2s,1d${)}^{24}$(1f,2p${)}^3$ and (2s,1d${)}^{23}$(1f,2p${)}^4$ configurational spaces were carried out using the WBMB spherical shell-model interaction. Energy spectra, nucleon pickup spectroscopic factors from ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$, two-nucleon transfer strengths from ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}$, and γ-ray transition rates were calculated for both ${}_{}{}^{43}{}_{}{}^{}\mathrm{K}$ and ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}$ as well as allowed and first-forbidden decays for the known branches in ${}_{}{}^{43}{}_{}{}^{}\mathrm{K}$(${\beta }^{\mathrm{-}}$) ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}$. Results are compared to experiment.

Described here is the use of a calibrated bremsstrahlung source to resolve conflicts in previous studies of the reaction ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$(γ,γ’${)}^{111}$${\mathrm{Cd}}^{\mathrm{m}}$ through a level located near 1200 keV. We report an integrated cross section of (9.8±2.5)×${10}^{\mathrm{-}29}$ ${\mathrm{cm}}^2$ keV with no evidence of any importance of nonresonant channels of excitation.

It is proposed that certain states of undetermined spin and parity observed in previously reported ${}_{}{}^{198}{}_{}{}^{}(\mathit{p}$,p’γ) and ${}_{}{}^{194}{}_{}{}^{}$,196,198Pt(p,p’) experiments are $3^{\mathrm{-}}$ states and contain a significant amount of octupole strength. These results show that the octupole strength is fragmented in the Pt isotopes. The predictions of Engel for the distribution of octupole strength in Pt isotopes are compared to the strengths obtained from (p,p’). Furthermore, an explanation for the anomalous behavior of $3_1^{\mathrm{-}}$ states in the Pt-Hg region is proposed.

Predictions for E2, M1, and M4 transition rates and moments, together with examples of transition-charge densities, are presented for states of N=50 nuclei. These predictions are based on one-body spectroscopic amplitudes obtained from the wave functions of a new N=50 shell-model calculation which incorporates the 0$f_{5/2}$, 1$p_{3/2}$, 1$p_{1/2}$, and 0$g_{9/2}$ single-particle orbits and an empirically determined effective Hamiltonian for this space. The predictions are compared with experimental data, first in order to evaluate how well the model space, as applied by this Hamiltonian, accounts for observations, and then to assess the importance of configurations excluded from the model space and to determine the values of the operator renormalizations (effective charges and effective g factors) which optimally map the theoretical results onto the corresponding experimental values.

The linear response of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nucleus to an external electroweak current is studied in a relativistic model. The relativistic form for the nuclear linear response is applied using the random-phase approximation, Dirac-Hartree single-nucleon orbitals obtained along with Lorentz-vector and scalar self-consistent meson mean fields, and various particle-hole residual interactions. Form factors for inelastic electron scattering are combined into complexes and compared with experiments and previous nonrelativistic predictions. The agreement with electron scattering experiments is of similar quality for both nonrelativistic and relativistic theories with no obvious signature obtained motivating the superiority of a relativistic treatment. For weak interactions, the relativistic approach yields a considerable variation in predictions depending on the residual interaction adopted and whether pseudovector or pseudoscalar πNN coupling is assumed.

Relativistic and nonrelativistic models in one dimension which simulate the deuteron and the ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ nucleon-nucleon (NN) scattering are constructed and the relation between the scattering length $a_t$ and the root-mean-square radius $r_m$ of the simulated deuteron is examined for a variety of interactions. The linear relation between $a_t$ and $r_m$, which was found by Klarsfeld et al. for realistic NN potentials, holds for a wide class of potentials, relativistic as well as nonrelativistic. Within the limitation of our one-dimensional models, this suggests that the discrepancy between theory and experiment which was pointed out by Klarsfeld et al. regarding $a_t$ and $r_m$ cannot be resolved by relativistic effects.

Although a number of different types of boson-fermion interactions are possible in the interacting boson-fermion model, empirical results have shown that the exchange term is of cardinal importance. A recently constructed similarity transformation which reexpresses the Dyson boson images of the single-j shell fermion operators in terms of seniority bosons is used to confirm that the origin of the exchange term in spherical nuclei is linked to the quadrupole pairing interaction between identical nucleons. The relative importance of the exchange and direct boson-fermion interactions is also discussed and it is indicated that the direct term is essential for a complete description of that excited state which carries the j value of the shell.

The M3 transition to the $K^{\pi }$${=1\mathrm{}}^{+}$ band describing the scissors mode is evaluated in schematic random-phase approximation for heavy deformed nuclei. The equivalence between this microscopic description of the mode and the one given within the classical two-rotor model is stressed. It is shown how such a schematic approach improves quantitatively the description of the mode with respect to the rigid two-rotor model and, in particular, provides more reliable values of the M1 and M3 strengths. A rough estimate of the importance of the spin versus the orbital contribution to the mentioned strengths is also made by carrying out the same schematic calculation in the neutron-proton formalism and using a Nilsson basis for ${}_{}{}^{164}{}_{}{}^{}\mathrm{Dy}$ chosen as representative of all nuclei in the rare-earth region. The spin contribution is found to be non-negligible but still quite small in both cases. The total M3 strength is smaller than the one predicted in the rigid two-rotor model and other approaches, but still observable. The possibility of actually observing such a transition in relation to the fragmentation of the strength is finally discussed.

A detailed study of the results of correcting BCS approximation for the effects of particle-number projection and blocking has been carried out. A low-seniority shell-model approximation was used as the frame of reference for investigating the mixing of one- and three-quasiparticle states in odd-mass Ni isotopes and in odd-mass N=82 isotones. We discuss the results obtained for the energy spectra and electromagnetic decay properties. Effects of seniority-five configurations on the low-lying states have also been studied through the comparison of the low-seniority shell-model results with those which arose from the corresponding full shell-model calculations.

The proton and neutron densities and nuclear potentials are calculated for the deformed sd-shell nuclei ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ in the framework of the constrained Hartree-Fock method and compared with the results of the spherical nucleus ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$. Coulomb core polarization effects are responsible for differences in the proton and neutron Hartree-Fock potentials. These charge-asymmetry effects in the nuclear mean field must be taken into account when trying to decide whether the charge asymmetry observed in proton and neutron scattering is due to a genuine charge asymmetry in the nuclear force and, if possible, to put an upper limit on the magnitude of this effect. Our calculations indicate that there is no enhancement of the charge asymmetry due to nuclear deformation. The often proposed volume integral of the nuclear potential is found not to be an appropriate tool to investigate charge-asymmetry effects in nuclei due to a large cancellation in the integral.

The gyromagnetic factors associated with the yrast levels (with $2^{+}$≤$J^{\pi }$≤${12}^{+}$) in some doubly even Ge and Se isotopes are discussed in a microscopic, parameter-free perspective in terms of the variational wave functions resulting from realistic effective interactions operating in the (2${\mathit{p}}_{3/2}$,2${\mathit{p}}_{1/2}$,1${\mathit{f}}_{5/2}$,1${\mathit{g}}_{9/2}$${)}^{\mathrm{gr}}$,ν configuration space. The estimates for the g factors of the yrast $2^{+}$ states are consistent with the available experimental results. The calculations reveal that the g factors for the high-spin states can provide important quantitative signatures vis-à-vis the occurrence of various structural changes in the anomalous yrast spectra in the germanium region.

The observed dramatic onset of large deformations in the highly neutron-rich Zr and Mo isotopes is examined by carrying out self-consistent Hartree-Fock-Bogoliubov calculations employing pairing-plus-quadrupole-quadrupole effective interactions operating in a reasonably large valence space outside an inert core. It turns out that the observed deformation systematics can be understood in terms of the polarization of the (2$d_{5/2}$${)}^6$ part of the N=56 core initiated by the involvement of the 1$h_{11/2}$ orbit in the underlying valence space. A variational calculation of the high-spin yrast spectra in the highly neutron-rich Mo isotopes suggests strongly the possibility of observing the backbending effect. It is also shown that the B(E2) values associated with the yrast spectra can provide unambiguous signatures of the large structural changes that are likely to occur in the high-spin yrast spectra of the nuclei in this new island of deformation.

The internal momentum spectrum of p+n pairs produced in the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(α,2α)pn reaction at 118 MeV was measured for those pairs whose c.m. was at rest after the reaction. This spectrum was calculated with a plane wave impulse approximation model, having no free parameters, for two $p_{3/2}$ nucleons initially bound in a harmonic oscillator potential. The calculation gave reasonable agreement with measured values of both the normalization of the spectrum and its dependence upon the p+n internal energy, when the final nucleons were described by Yamaguchi, Paris, or Reid wave functions and the data were reduced by the final-state energy prescription. Less satisfactory fits were obtained with p+n plane waves and/or the initial-state energy prescription.

Isomeric ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ge}$ nuclei were populated by a heavy-ion reaction and separated by a recoil mass spectrometer. The nuclear spin alignment produced by the reaction and preserved through the separation process was studied for Ar-like q=+14 Ge recoils by observing the anisotropy of decay gamma rays. An $A_2$ coefficient of 0.029(14) was measured, corresponding to preservation of 15(8)% of the initial alignment. This result opens a new avenue in the study of nuclear static moments of long-lived isomers using recoil mass spectrometers.

The odd-even staggering of the differential radii of Fr and Ra and the Cs and Ba nuclei is compared. This staggering is inverted in the region of known octupole deformation in the Fr and Ra nuclei. The normal staggering is eliminated in the Cs nuclei and attenuated in the Ba nuclei for neutron numbers 85–88. This fact is used to suggest the possible existence of octupole deformation and its neutron number range in the Cs and Ba nuclear ground states.

We test a new time-dependent method to compute proton-proton scattering using the Graz plus Coulomb potential.

Excitation functions for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C elastic scattering have been calculated in the center-of-mass energy range $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=15 to 95 MeV at c.m. angles of 50°, 70°, and 90° using optical-model parameters determined by fitting an angular distribution at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=60.8 MeV. Conventional Woods-Saxon parameters for four families of different real well depth and with either a volume or surface absorption predict gross structure at 90° which persists undiminished throughout this energy range.

It is pointed out that the nonunitary generalized Dyson mapping, which does not preserve Hermitian conjugation, is not necessary in order to obtain finite images of shell-model operators. Unitary mappings, which do preserve Hermitian conjugation, have long been available but largely overlooked.

A statistical model has been developed to compute total pion production cross sections at energies below the energy threshold for pion production in free nucleon-nucleon collisions. The model assumes that during a collision between two nuclei a fraction of their energy is released within an interaction volume and is rapidly distributed among the different degrees of freedom. The calculation of the probability of creating a pion is based on the statistical weights of the various possibilities. The model has been applied successfully to reactions between ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ projectiles and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, W, and U targets for energies ranging from 25 to 84 MeV/nucleon.