The photofission cross section of natural Bi was measured in the energy range 100–300 MeV by means of a quasi-monochromatic photon beam. The nuclear fissility $P_f$ was calculated using the recently measured total photoabsorption cross sections. A discussion on the dependence of fissility from the excitation energy $E_x$ shows that a linear dependence of ln$P_f$ vs $E_x^{\mathrm{-}1/2}$ can hardly be assumed over all the considered energy range. The analysis of the data confirms this consideration and shows an evident saturation effect at high excitation energy. As a consequence, in disagreement with recent interpretations, inferring that the modified quasi-deuteron model is the only efficient mechanism in inducing fission of Bi is less compelling, and also the pion photoproduction excitation mechanism plays a role.

The present work is a study of Δ production in proton-nucleus collisions at intermediate energies. The theory is based on the Glauber multiple scattering theory. For the elementary NN→ΔN process, we employ the amplitude decomposition by Silbar et al. and by Auger et al. The numerical values of the parameters involved are taken from the work of Kloet and Silbar. Two specific examples of nuclear targets are examined: ${\Delta }^{++}$ production in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ at 800 MeV. The effects of multiple scattering corrections on selected spin observables are studied in detail. In light of our results we discuss the possibilities of using nuclear reactions to obtain information on specific production amplitudes and on Δ propagation through the nuclear medium.

Energy spectra of products with A=47–143 emitted at 90° to the beam in the interaction of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ with 400 GeV protons were obtained from measured differential ranges. The products can be divided into two groups: those showing a single dominant energetic component and those with an additional low-energy component. The energetic component was fit with a thermal fragment emission model and is consistent with binary fission and, for the lightest products, with fragmentation. The low-energy component is consistent with a deep spallation mechanism.

Differential cross sections for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p,${\pi }^{+}$${)\mathrm{}}^{13}$${\mathrm{C}}^{\mathrm{*}}$ reaction at $T_{\mathrm{p}=250\mathrm{}}$, 354, and 489 MeV are presented and compared with previously published data taken at other energies in the ${\Delta }_{1232}$ resonance region. At fixed four momentum transfers greater than 0.4 ${\mathrm{GeV}}^2$/$c^2$, the differential cross sections exhibit a maximum near the invariant mass of the ${\Delta }_{1232}$. This energy dependence is similar to that shown by the pp→d${\pi }^{+}$ reaction at equivalent energy, and provides strong evidence of a NN→NN${\pi }^{+}$ process in the (p,${\pi }^{+}$) reaction mechanism. The total cross section for each transition exhibits a maximum at an energy about 100 MeV lower than that expected from the ${\Delta }_{1232}$ invariant mass. This energy dependence could be the result of an interplay between the increase in cross section due to the role of the ${\Delta }_{1232}$ in the (p,${\pi }^{+}$) reaction mechanism, and the decrease in cross section due to the large momentum transfers that the reaction is restricted to at higher energies.

Total reaction cross sections have been measured for 50 and 65 MeV ${\pi }^{\pm }$ on C, O, ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, S, Ca, and Zr. The motivation for this experiment is to obtain cross sections to act as constraints in optical model fits to elastic scattering data. Measurements using the ‘‘poor geometry’’ transmission method were made for exceptionally small angles with the aim of improving the accuracy of the extrapolation to zero solid angle. At these small solid angles the muon cone from pion decay contributes significantly and its effects were explicitly included. The accuracies of the elastic correction are evaluated by using error matrix techniques and an additional systematic error is included.

Differential cross sections were measured for pion elastic and inelastic scattering from ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$ at $T_{\pi }$=180 MeV. Elastic scattering data were analyzed using a standard Kisslinger potential. Inelastic scattering data were analyzed using distorted-wave impulse-approximation calculations with collective-model transition densities. Ground-state neutron-density parameters and matrix elements for some of the transitions were extracted.

Deep inelastic structure functions are derived in the hybrid quark-hadron model with three methods for including binding. With light-front dynamics, the European Muon Collaboration effect is shown to be consistent with this model, with an internal six-quark structure region of average probability of about 20% in medium-mass nuclei, as found in exclusive electron scattering on light nuclei; while instant-form dynamics is not consistent with the model.

A complete set of Lorentz invariant nucleon-nucleon amplitudes, based on a meson-exchange model and on-mass-shell kinematics, is used to construct the impulse approximation optical potential for use in the Dirac equation. Relativistic nuclear densities are also used in the construction. No free parameters enter. The analysis provides a dynamical basis for the virtual pair couplings which are implicit in the Dirac equation for proton-nucleus scattering. A momentum space potential and a localized potential suitable for coordinate space analysis are developed. Initial numerical calculations are presented for proton scattering by ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 200, 500, and 800 MeV. The generalized impulse approximation provides a successful description of the elastic scattering data for these cases. Low energy results are improved substantially in comparison with the original form of Dirac impulse approximation based on using five Fermi amplitudes to represent nucleon-nucleon scattering.

For use in applications such as pion photoproduction and inelastic exclusive pion scattering studies, a first-plus-second-order pion-nucleus optical potential is constructed by fitting the phenomenological ${\rho }^2$-dependent term to the ${\pi }^{\pm }$${\mathrm{-}}^{12}$C total and differential cross sections. It is demonstrated that such a potential is A universal (A is the atomic mass number) and well describes all available (total and elastic differential) pion scattering data for the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ targets in a broad energy range 14≤$T_{\pi }$≤250 MeV.

The decay of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Sr}$ (193 ms) to the low-spin ${}_{}{}^{100}{}_{}{}^{}\mathrm{Y}$ isomer (735 ms) was studied from mass-separated activity produced in thermal neutron fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$. γ singles and γ-γ coincidence measurements resulted in the placement of 67 γ transitions in a decay scheme with 26 levels below 2 Mev. The multipolarities of low-energy transitions were determined from internal conversion electron measurements. Logft values were deduced using an absolute γ-ray intensity determination for the A=100 decay chain. The $1^{+}$ levels in ${}_{}{}^{100}{}_{}{}^{}\mathrm{Y}$ at 10.70 and 974.61 keV each receive ∼40% of the β feeding from ${}_{}{}^{100}{}_{}{}^{}\mathrm{Sr}$. A $K^{\pi }$${=1\mathrm{}}^{+}$ rotational band (with $1^{+}$, $2^{+}$, and $3^{+}$ levels at 10.70, 76.15, and 172.03 keV) is proposed which can be characterized as a nearly ‘‘pairing-free’’ band. Other levels in ${}_{}{}^{100}{}_{}{}^{}\mathrm{Y}$ are discussed in terms of two-quasiparticle Nilsson orbitals.

Strong E0 lines from the 4866 and 5237 keV $0^{+}$ states in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been identified using a new high-energy conversion-electron spectrometry technique in the study of the ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$(d,p${)}^{208}$Pb and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$(p,p’${)}^{208}$Pb reactions at $E_{\mathrm{d}=10\mathrm{}}$ MeV and $E_{\mathrm{p}=17.3\mathrm{}}$ MeV, respectively. No evidence for an E0 transition from the expected third $0^{+}$ state was found.

We produced carrier-free, nearly isotopically pure ${}_{}{}^{193}{}_{}{}^{}\mathrm{Ir}_{}^{\mathrm{m}}{}_{}{}^{}$ from thermal-neutron irradiation of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$. From studies of the conversion-electron spectrum, the photon spectrum, and the absolute counting rates, we determined the absolute K, L1, L2, L3, M1, M3, M5, N, and O+P conversion coefficients for the first time. With possibly one exception, these values agree closely with theoretical calculations. The value for the energy of the unconverted gamma ray was found to be 80.22±0.02 keV. The half-life for ${}_{}{}^{193}{}_{}{}^{}\mathrm{Ir}_{}^{\mathrm{m}}{}_{}{}^{}$ determined by absolute electron counting in a proportional counter of 100% counting efficiency (4πβ) was found to be 10.53±0.04 d. We have determined the $L_1$ subshell fluorescence yield, ${\omega }_1$, to be 0.120±0.003 for iridium. Based upon our measurements of initial and final L subshell vacancies together with a best-fit literature value for ${\omega }_2$, we have found a plausible value for the Coster-Kronig coefficient $f_{12}$ to be 0.091±0.011.

Variational bounds for the Reid soft core and Argonne $V_{14}$ potentials are extended through the J=8 partial waves of those nucleon-nucleon forces using Faddeev wave functions calculated with the J≤4 partial waves. We verify our previous conjecture that the additional components add roughly 10 keV to the binding energy, and that the convergence of the binding energy with respect to the nucleon-nucleon partial-wave angular momentum is roughly geometrical.

It is argued that the charge dependence of the nuclear force ($V_{\mathrm{nn}\mathrm{\ne }{V}_{\mathrm{np}{}^s}}$) can be accounted for exactly in triton binding energy calculations to first order in the difference $V_{\mathrm{nn}\mathrm{-}{V}_{\mathrm{np}{}^s}}$ by replacing the ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$ interaction by the potential combination (2/3$V_{\mathrm{nn}+1)/3V_{\mathrm{np}{}^s}}$. .AE

Isovector pairing collective motion is treated by means of the generator coordinate method. In this scheme, the isospin and number projection is performed analytically by the recognition of symmetry properties in the generalized Bardeen-Cooper-Schrieffer wave functions. Among the results obtained, our generator-coordinate-method values of energy and spectroscopic amplitude are shown to be comparable to those of shell model calculations. This is indeed encouraging, especially in view of the fact that they were reached using a simple approximation. The great simplicity of the present method, as compared with earlier complicated versions, suggests that they might prove useful in the study of isovector pairing collective states which are strongly populated by pair transfer reactions in medium weight nuclei.

A fermion dynamical symmetry model is presented. The model has a rich variety of dynamical symmetries, with fully microscopic connections between these dynamical symmetries and the underlying shell structure. In the low angular momentum region, without explicit introduction of bosons, all the dynamical symmetries contained in the phenomenological interacting boson model are recovered. Furthermore, the model predicts several new dynamical symmetries, one of which has recently been empirically verified, and has limits appropriate to the study of high-spin physics.

The hybrid soliton model describes nucleons as consisting of quarks and pion and sigma meson fields. We place these nucleons on a three-dimensional lattice and calculate the dependence of the total energy on the density. Various higher order terms in the meson fields are implemented into the Lagrangian of the model to change the behavior of the interaction energy between the nucleons. Because of the increase in quark kinetic energy at higher densities, we have not been able to obtain a minimum at ground state nuclear density.

Optical model and exact finite range distorted-wave Born approximation analyses were performed on neutron pair exchange and alpha particle exchange reactions between two identical colliding cores. The possibility of a nuclear Josephson effect is discussed.

From the pulse-height spectrum from a ${\mathrm{BF}}_3$ proportional counter exposed to water-moderated ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ neutrons, the thermal cross section for the reaction ${}_{}{}^{10}{}_{}{}^{}\mathrm{He}$ is determined to be 7±2 mb.

The measured yield of the ${(39/2\mathrm{}}^{\mathrm{-}}$ isomer in ${}_{}{}^{211}{}_{}{}^{}\mathrm{At}$ from the reaction ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$(α,2n) indicates angular momentum saturation at 44–48 MeV of incident alpha energy. The average angular momentum in the evaporation residue ${}_{}{}^{211}{}_{}{}^{}\mathrm{At}$ is estimated to be 18ħ.