Two mini-orange spectrometers were used to view ${\mathrm{e}}^{+}$-${\mathrm{e}}^{\mathrm{-}}$ pairs from a positron source and a Th scatterer from opposite directions, 180° apart. No statistically significant evidence for peaks previously reported was found in the coincidence spectra.

Elastic cross sections for the scattering of negative pions from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were measured at 19.5 and 30 MeV incident pion energy. At both energies the new cross sections show fair agreement with optical model predictions. At 30 MeV the new cross sections disagree at forward angles with previously measured values, while at 19.5 MeV the data represent the first report of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ${\pi }^{\mathrm{-}}$ scattering at this energy.

Conversion-electron measurements following the ${}_{}{}^{144}{}_{}{}^{}(\mathit{\alpha }$,2n) and ${}_{}{}^{144}{}_{}{}^{}\mathrm{He}$,n) reactions reveal high-energy E0 transitions at 3020, 3485, and 3639 keV. The lowest of these deexcites the known two-neutron pairing vibrational state in ${}_{}{}^{146}{}_{}{}^{}\mathrm{Gd}$. It is not clear whether either of the others can be associated with the $0^{+}$ member of the $3^{\mathrm{-}}$×$3^{\mathrm{-}}$ two-phonon octupole multiplet.

The absolute value of the vector analyzing power, ‖${\mathrm{iT}}_{11}$‖ has been measured for elastic scattering of 150-MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at ${\theta }_{\mathrm{lab}=7.7\mathrm{}}$° from the observation of the left-right asymmetry in double scattering. A magnetic spectrograph was applied for focusing elastically scattered particles ejected from the first target onto the second one. The deduced ‖${\mathrm{iT}}_{11}$‖ was ‖${\mathit{iT}}_{11}$‖=($2_{\mathrm{-}2}^{+11\mathrm{}}$)×${10}^{\mathrm{-}2}$. The observed value was reproduced within the experimental errors by a cluster folding coupled channel calculation involving the effect of projectile excitations.

The various contributions to the deuteron bremsstrahlung-weighted photonuclear sum rule ${\sigma }_{\mathrm{-}1}$ are analyzed. It is shown that the unretarded normal L=1 sum rule is model independent and that retardation, higher multipoles, and interaction effects are negligible. An accurate estimation of ${\sigma }_{\mathrm{-}1}$ is provided by the knowledge of the charge deuteron radius and of the spin gyromagnetic factors of the proton and of the neutron.

The effects of different ingredients of time-dependent dynamical simulation models are investigated. The variable of interest is the net ${\pi }^{\mathrm{-}}$ production. I study the Ar+KCl data from $E_{\mathrm{lab}}$=0.36 to 1.808 GeV/nucleon with the momentum-dependent Boltzmann-Uehling-Uhlenbeck approach. Implications for the determination of the nuclear equation of state are mentioned and limitations of the model are considered.

Charge symmetry violation due to the Coulomb force in the elastic scattering of ${\pi }^{\pm }$ from ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is studied using a theoretical optical potential with spin. Our calculated results compare favorably with the experimental differential cross sections of Källne et al. and of Nefkens et al., indicating that the observed violation of the charge symmetry can be due to direct Coulomb effects.

Using the angular momentum projection approach with the $l^2$-depressing parameter ${\mu }_{\mathrm{p}}$ in the Nilsson model reduced by 15%, the band heads of the $0_2^{+}$, $0_3^{+}$, and $0_4^{+}$ bands in ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$ are calculated to lie at 1221, 1426, and 1823 keV, respectively, in good agreement with recent experimental data. An additional low-lying $0^{+}$ band with a band head at 1966 keV is also predicted. A general criterion for the existence of a low-lying $0^{+}$ excited band is described and invoked to substantiate the calculated results.

The structure of the even-even Te nuclides with 114<A<134 is shown to consist of features that can be associated with underlying low-energy collective excitations, as well as particle-hole intruder and two-quasiparticle configurations. Energy level positions and branching ratios from new and existing measurements can be reasonably well fitted with a proton-neutron interacting boson model calculation that includes particle-hole configuration mixing. After identifying levels that have large particle-hole intruder admixtures, little evidence for structures closely resembling those of the O(6) or SU(5) dynamical limits can be found.

Microscopic cluster models for A=3–9 are calculated with use of Gaussian-type ΛN and ΛNN interactions. Use of the strongly repulsive ΛNN interactions makes it possible to reproduce systematically Λ binding energies of s-shell and light p-shell hypernuclei. In the case of ${}_{\mathrm{\Lambda }}{}^{16}{}_{}{}^{}\mathrm{O}$ the ΛN+ΛNN interaction produces results similar to a density-dependent ΛN interaction.

We present the first global relativistic optical-model treatment of proton-nucleus elastic scattering. Energy-dependent optical potential parameters for the Lorentz vector and scalar potentials of Dirac phenomenology are given. Several different assumptions regarding the optical-model energy dependence are considered. Constraints from relativistic mean-field theory are presented.

High spin states in ${}_{}{}^{174}{}_{}{}^{}\mathrm{Ta}$ have been studied for the first time through in beam spectroscopy techniques following the ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$(${}_{}{}^9{}_{}{}^{}\mathrm{Be}$,4n) fusion-evaporation reaction. A $\Delta I=2\mathrm{}$ doubly decoupled band based on a $3^{+}$ state has been searched for and identified, confirming the predicted deformation dependence of this structure. A remarkable additivity is found for alignments and deviations of moments of inertia with respect to an appropriate even-even core.

In order to test whether entrance-channel effects influence the production of superdeformed nuclei, the yields of the discrete superdeformed band in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ are compared for three projectile-target combinations. No evidence for entrance-channel effects is found. Rather, the population of this band seems to be determined by the excitation energy and maximum angular momentum brought in by each reaction.

In this paper we present a nonrelativistic microscopic mean-field framework for finite nuclei in which the nucleus is described as a collection of nucleons and $\Delta (3, 3)$ resonances. The ground-state properties of the nuclei ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are determined within the spherical Hartree-Fock approximation using a realistic effective no-core Hamiltonian in a basis consisting of up to six major oscillator shells. A detailed study of the zero-temperature properties of these nuclei under compression and dilation is presented in order to gain insight into the nuclear equation of state. Under certain conditions, a transition to a mixture of nucleons and deltas is found in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ but not in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. The transition is reminiscent of a first-order phase transition.

Differential cross sections have been measured for the reaction ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$(γ,${\mathrm{n}}_0$${)}^{17}$O over the region of excitation energy from 14 to 26 MeV. The angle-integrated cross section for the ground-state transition reveals that this channel accounts for less than 20% of the total photoneutron cross section in the structured pygmy resonance region (near 14 MeV) and is a small fraction (10–15 %) of the cross section in the region of the giant resonance (near 25 MeV). The values of angular distribution coefficients fitted to the data are consistent with a description of this reaction in which electric dipole excitations dominate the cross section in the pygmy resonance. Narrow regions exist near 15.0, 16.0, and 20.0 MeV where nonzero $a_1$ coefficients are observed indicating the absorption of non-E1 radiation. The measured cross section and $a_2$ coefficients are compared to a direct-semidirect calculation which gives reasonable agreement and suggests that f-wave neutron emission dominates the ground-state channel and that there is little justification for the introduction of E2 amplitudes other than a pure direct E2 term.

The E1 and E2 components of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(α,γ${)\mathrm{}}^{16}$O S factor are investigated microscopically with a generator-coordinate calculation involving α${+\mathrm{}}^{12}$${\mathrm{C}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$, α${+\mathrm{}}^{12}$C($2_1^{+}$), p${+\mathrm{}}^{15}$${\mathrm{N}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$, and n${+\mathrm{}}^{15}$${\mathrm{O}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ configurations. The theoretical capture cross sections towards the ground state and excited states are in semiquantitative agreement with experiment. Simple corrections to the microscopic expressions lead to good agreement with experimental data. The corrected model provides an S factor of 0.24 MeV b at the astrophysically important energy 0.3 MeV.

The electromagnetic deexcitation of the six known ${}_{}{}^{14}{}_{}{}^{}$C+α resonances in the range $E_{\alpha }$=1.7–2.7 MeV was observed with a Ge(Li) detector. Results for the branching ratios of the 7.62-, 8.04-, and 8.13-MeV ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ levels were found to be in agreement with previous measurements. Deexcitation of the 7.86-, 8.21-, and 8.28-MeV levels was observed for the first time. The radiative widths of these three (α,γ) resonances were determined. Electromagnetic transition strengths were derived for all the resonances from the gamma-ray branching ratios and the total radiative widths. A selective and enhanced E1 decay (∼${10}^{\mathrm{-}2}$ W.u.) of the $3_3^{\mathrm{-}}$ state is observed; among the available $2^{+}$ states lower in excitation, this $3_3^{\mathrm{-}}$ state is observed to deexcite only to the $2_3^{+}$ state. The $2_3^{+}$ state is well understood to involve excitations of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ core, whereas the $2_2^{+}$ and $2_1^{+}$ states arise mainly from simple two neutron (sd-shell) configurations. The relevance of the α${+\mathrm{}}^{14}$C radiative capture reactions for nucleosynthesis of heavier elements, at the hadronization phase of the big bang, is discussed.

Inclusive spectra of ${(}^3$He,t) on ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ have been measured and analyzed in a large energy range of emitted tritons at $E_{{\mathrm{}}^3\mathrm{He}=90\mathrm{}}$ MeV in the angular range 7°–27°. The spectra have been analyzed in terms of a superposition of simultaneous breakups, quasifree reactions, and two-step-fragmentation plus pickup processes. The residual spectra correspond to excited states in ${}_{}{}^9{}_{}{}^{}\mathrm{B}$. Confirmation for uncertain states was obtained. Some new states, possible analogs to ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, were observed.

Both the variational approach and the method of separable expansion have proved to be very useful for the solution of scattering equations. Connections are established between these two approaches. It is shown that an underlying variational principle is responsible for the good convergence obtained with the method of separable expansions. It is pointed out that a proper choice of expansion functions is essential for the rapid convergence of the method of separable expansion. Several types of separable expansions are tested numerically for the Reid ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$ soft-core potential. It is shown that with proper choices of expansion functions these separable expansions yield more rapid convergence than those obtained previously in other studies of separable expansions. In the case of the three-body scattering equations the usual separable expansions are shown to follow from the general expansion schemes studied here with special choices of expansion functions.

The photoneutron cross sections for ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Pb}$ have been measured near the peak of the giant dipole resonance, with monoenergetic photons, in such a way that the absolute cross sections for these nuclei were intercalibrated, using ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$ as a benchmark. The measured peak total photoneutron cross sections are, within an uncertainty of 2–3 %, 174, 252, 340, 502, and 602 mb for ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Pb}$, respectively. These results resolve outstanding discrepancies among previous measurements.