Cross sections for photon elastic scattering have been measured for ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ between 4.8 and 6.4 MeV with an energy resolution of about 50 keV. These data have been used along with existing photofission data to infer the total photoabsorption cross section ${\sigma }_T$ and the fission transmission coefficient $T_f$ below neutron threshold. We find that the inferred ${\sigma }_T$ varies smoothly with energy and generally follows the extrapolated tail of the giant dipole resonance, and that $T_f$ shows a broad bump between 5.6 and 5.9 MeV. These results strongly support the contention that resonances seen in near-threshold photofission cross sections are due to the fission and not the photon channel .

Neutron differential-elastic-scattering cross sections of bismuth were measured at ≊0.5 MeV intervals from ≊4.5 to 10.0 MeV. At each incident energy 40 or more differential values were obtained between ≊18° and 160°. These data were combined with lower-energy results previously reported from this laboratory, and others available in the literature, to provide a detailed data base extending from ≊1.5 to 10.0 MeV. This data base was interpreted in terms of the conventional optical-statistical model and also using a model which included the surface-peaked real potential predicted by the dispersion relation. Particular attention was given to the energy dependence of the volume-integral-per-nucleon of the real potential, $J_v$, to see if there was evidence of the Fermi surface anomaly. In the range 3.0–10.0 MeV, the present study indicates that ${\mathrm{dJ}}_v$/dE is essentially constant, with a relatively large negative value of -6.0 to -9.0 ${\mathrm{fm}}^3$, depending on the model used in the analysis. Below 3.0 MeV, there is some evidence for a decrease in the magnitude of ${\mathrm{dJ}}_v$/dE. However, the effect is very small, and it is only when this trend is combined with considerations of the $J_v$ values needed to give correct bound-state energies that evidence for the Fermi surface anomaly emerges. $J_v$ and the geometry of the optical potentials found for ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ become equal to those explaining the higher-energy ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ data at about 10.0 MeV. Since ${\mathrm{dJ}}_v$/dE for the latter is smaller in magnitude than that for ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$, a change in ${\mathrm{dJ}}_v$/dE is clearly indicated near 10.0 MeV.

A set of parameters has been derived for a global optical potential from elastic α-nucleus scattering with energies higher than 80 MeV. The geometry and energy dependence derived by Put and Paans was adopted. The optical model predictions were tested with data from elastic as well as from inelastic scattering.

Cross sections of inelastic α-particle scattering to isovector giant dipole resonances are calculated including both nuclear and Coulomb excitation. It is shown that the calculated cross sections are rather small and can be safely neglected for bombarding energies less than 200 MeV in determining the strength of the giant monopole resonance. This conclusion contradicts that of a recent report made by Peterson.

Energy spectra of protons emitted from (p,p’) scattering were measured for ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$, ${}_{}{}^{92}{}_{}{}^{}$,94,96,98,100Mo, ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$, and Ag at an incident energy of 18 MeV. It was shown that there were no appreciable shell and odd-even effects on the preequilibrium proton spectra corresponding to excitations higher than 4 MeV of the residual nucleus. The experimental results were interpreted on the basis of the state densities generated from two sets of single particle levels using the recursion method by Williams et al.; one is based on the spherical Nilsson model, and the other on the modified uniform spacing model in which a shell gap is introduced into the uniform spacing model. The measured angle-integrated proton spectra were compared with those calculated on the basis of the exciton model and the Hauser-Feshbach model in which the isospin selection rule was taken into account. Good agreement between the experimental and calculated spectra was obtained for all targets in the continuum region in the outgoing proton energy region of 3–14 MeV.

Proton and alpha emission in ${}_{}{}^{20}{}_{}{}^{}$Ne${+\mathrm{}}^{24}$Mg collisions have been measured at $E_{\mathrm{lab}=55\mathrm{}}$, 80, and 160 MeV in an angular range of 0°≤${\theta }_{\mathrm{lab}<150\mathrm{}}$°. The experimental results were confronted by models for compound nucleus deexcitation. Satisfactory agreement is found if angular momentum conservation is taken explicitly into account. The contribution of preequilibrium process is also examined.

Using aligned ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ beams, fusion cross sections ${\sigma }^{\mathrm{fus}}$ and second-rank tensor analyzing powers for fusion $T_{20}^{\mathrm{fus}}$ have been measured at energies near and below the fusion barrier for ${}_{}{}^{23}{}_{}{}^{}$Na${+\mathrm{}}^{48}$Ti and for ${}_{}{}^{23}{}_{}{}^{}$Na${+\mathrm{}}^{206}$Pb. At sub-barrier energies, large, nearly maximal, values of $T_{20}^{\mathrm{fus}}$ occur, especially for fusion with the heavy target ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$. This reflects the strong influence of the spectroscopic deformation of the projectile on the fusion process at energies below the barrier. However, within a quantum-mechanical coupled-channels calculation this degree of freedom is not enough to describe both the fusion cross section and the second-rank tensor analyzing power for fusion in the energy regime below the fusion barrier. It is shown that the coupling of the fusion channel to inelastic excitations of the projectile and the target can describe the magnitude and energy dependence of $T_{20}^{\mathrm{fus}}$ for both heavy ion systems, but fails to reproduce the ‘‘sub-barrier enhancement’’ of the fusion cross section for both systems.

The reaction ${}_{}{}^{32}{}_{}{}^{}$S${+\mathrm{}}^{182}$W has been studied at beam energies of 166, 177, 222, and 260 MeV with the goal of accounting for the distribution of the total reaction cross section among the main reaction channels. Cross sections as well as mass and energy distributions were measured over the entire angular range from 10° to 170° for elastic (which includes quasi-elastic), deep-inelastic, and fission-like products. Deep inelastic scattering accounts for a substantial fraction of the total reaction cross section at all energies, in particular near the barrier. This behavior is not predicted by current theories such as the extra push model. The angular distributions of fission-like products are more anisotropic than expected on the basis of the saddle point model at the two lowest energies, indicating a sizable contribution from quasi-fission processes, which is estimated from a quantitative analysis of this deviation.

The origin of the oscillations in the fusion excitation function for the ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{12}$C system is investigated in the framework of the optical model using the concept of internal and barrier waves. It is found that the oscillations are caused by the interference of internal and barrier waves, which satisfy a destructive interference condition. The internal wave also plays an important role in reproducing the correct magnitude of the fusion cross section.

Excitation functions of deep-inelastic scattering and fission have been measured for ${}_{}{}^{58}{}_{}{}^{}{+\mathrm{}}^{112}$,124Sn at bombarding energies between 230 and 290 MeV. It is found that even at energies below the Coulomb barrier deep-inelastic scattering is an important reaction channel with yields similar to that of fusion. The total reaction cross sections are now in good agreement with the sum of the measured fusion, deep-inelastic, and quasielastic scattering yields. Attempts to reproduce the sub-barrier fusion yields by coupled-channels calculations are discussed.

We have explored the viability of incoherent npγ bremsstrahlung as the dominant mechanism for the production of high energy γ rays in heavy-ion collisions by comparing the calculated relative angular distributions with experimental results. We have utilized the Boltzmann master equation model of heavy-ion collisions to decompose the reaction into first- and higher-order collision components in the assumed nucleon-nucleon cascade of the relaxation process. Within this decomposition we treat the γ-ray angular distribution of the first collision component by adopting a semiclassical npγ bremsstrahlung formula. The multiple collision component is assumed to contribute isotropically in the nucleus-nucleus center-of-mass system, and the Boltzmann master equation model enables us to weight these two components relative to one another. We then compare the predictions of our model with the available experimental results, finding generally favorable agreement between model and data. Within the uncertainties of our calculation and the data, the predicted angular distributions are consistent with an incoherent npγ bremsstrahlung mechanism as the source of high energy γ rays in intermediate energy heavy-ion collisions.

We have observed incomplete momentum transfer in binary reactions of the ${}_{}{}^{40}{}_{}{}^{}$Ar${+\mathrm{}}^{58}$Ni system at 15 MeV/nucleon with a relative intensity of 0.11±0.05. The projectile spectator has a mass close to A=8, and the inelasticity of reactions with incomplete momentum transfer is halfway between that of normal elastic and deep-inelastic reactions.

The standard form of the optical limit of the Glauber model used for the description of elastic scattering is modified to account for the Coulomb distortion of the trajectory occurring in the case of heavy ion scattering at relatively low bombarding energies. We retain the description of the process in terms of nucleon-nucleon collisions, but we relate the nuclear density overlaps for each partial wave to the distance of closest approach of the associated Rutherford trajectory, rather than to the asymptotic value of the impact parameter. Parameter-free predictions for the elastic scattering of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ at 390 MeV and of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ at 1760 MeV from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, based on experimental nucleon-nucleon total cross sections and standard densities, show a remarkable improvement for both differential and reaction cross sections. The consistency of the approach is strengthened by a correlated method for the inversion of the phase shifts, which, for the examined cases, yields optical potentials very similar to those obtained by optical-model fit analysis.

We show that it is possible to derive the real parts of the low-energy optical potentials for the systems ${}_{}{}^{16}{}_{}{}^{}$O${+\mathrm{}}^{16}$O, ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{12}$C, and ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{16}$O simultaneously from a single effective interaction by means of the double-folding model. However, this effective interaction does not produce satisfactory results at high energies. In contrast, the effective interaction of Satchler ane Love gives satisfactory results in both regions and can be regarded as reference potential over a wide energy range.

Angular distributions of the spin observables $A_{\mathrm{nn}}$, $A_{\mathrm{no}}$, and $A_{\mathrm{on}}$ for the reaction pp→d${\pi }^{+}$ have been measured for pion c.m. angles 30°<${\theta }_{\pi }^{\mathrm{*}}$<110° at beam kinetic energies of 500, 600, 650, 700, 733, and 800 MeV. These are precision data spanning the energy region of two conjectured dibaryon resonances in the NN system, one near 650 MeV ${(}^1$${\mathrm{D}}_2$) and one near 750 MeV ${(}^3$${\mathrm{F}}_3$). The $A_{\mathrm{nn}}$ data have a significant impact on the partial-wave analyses and are in disagreement with the predictions of existing models. The data show no direct evidence for the existence of either of the two dibaryon resonances.

Up to the highest momentum transfer measured [≃2 (GeV/c${)}^2$], the inelastic double differential α-nucleus cross sections obtained with α’s of 7 GeV/c incident momentum are fairly well described by an incoherent sum of single and double quasielastic collisions on the substructures of the target, and the different orders of scattering are clearly identified. The assumptions used in this analysis are also justified by the elastic behavior of the integrated partial cross sections that correspond to these different orders of scattering. The interpretation of these integrated cross sections by a Glauber model enables the evaluation of the mean square radii as well as the spectroscopic factors of the substructures concerned. Pion processes measured in these α-nucleus collisions are also considered.

Spin polarization and spin alignment of angular momenta in hypernuclei are discussed in terms of a distorted wave Born approximation. Hypernuclei produced by (${\pi }^{+}$,${\mathrm{K}}^{+}$) and (${\mathrm{K}}^{\mathrm{-}}$,${\pi }^{\mathrm{-}}$) reactions are shown to have sizable amounts of polarization and alignment. They are promising for use in spectroscopic studies of electromagnetic transitions, electromagnetic moments, and weak decays of hypernuclear states.

The collective excitation of the natural parity states in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Yb}$ has been studied with 36 MeV α particles. An analysis of the ground-state band data through $I^{\pi }$${=6\mathrm{}}^{+}$ gave deformation parameters ${\beta }_2$=+0.21±0.01, ${\beta }_4$=-0.028±0.004, and ${\beta }_6$=0±0.002. Two $K^{\pi }$${=2\mathrm{}}^{+}$ bands, with band heads at 1465 and 1608 keV, and the β vibrational $K^{\pi }$${=0\mathrm{}}^{+}$ band with a $2^{+}$ state at 1118 keV are excited weakly. Other $2^{+}$ states at 2184, 2255, 2367, 2465, 2580, 2650, 2738, 2836, 2890, and 2955 keV are seen, and their isoscalar strengths are found for the first time. The B(E2) strengths found are roughly in agreement with interacting boson model predictions close to the SU(3) limit. At 1263 keV, the $4^{+}$ state of the $K^{\pi }$${=3\mathrm{}}^{+}$ band is found to have an isoscalar E4 strength=0.036 $e^2$${\mathrm{b}}^4$ (7 single particle units). A compilation plus reanalysis of earlier data exhibits unexpectedly strong E4 strength to the $4^{+}$ members of the lowest K${=2\mathrm{}}^{+}$ and $3^{+}$ bands in strongly deformed rare earth nuclei. The octupole strength in this nucleus lies mainly in four $3^{\mathrm{-}}$ states at 1222, 1710, 1822, and 2030 keV with total isoscalar E3 strength of 0.147 $e^2$${\mathrm{b}}^3$. The results for the negative parity states are compared with the theory of Neergärd and Vogel.

Forward-angle differential cross sections for pion single-charge exchange to the isobaric-analog state were measured for ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$ at 20 MeV incident beam energy. Back-angle differential cross sections for ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ were also measured. The shape of the angular distributions for light nuclei is featureless. The cross section for ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ at 180° is as large as the cross section at 0°. The A dependence of the 0° cross section can be expressed as g(N-Z)$A^{\alpha }$ (with g=534 and α=0.73±0.09), leading to the conclusion that the nuclear medium is neither strongly absorbing nor fully transparent. The data are compared with optical-model calculations.

Within a unitary πNN theory a set of coupled integral equations defined in the NN⊕NΔ ⊕πNN subspace has been derived for examining the extent to which the NN and πd elastic scattering data can be both described by a class of meson-exchange πNN models. The considered models are constructued by using a previously developed subtraction procedure to extend the Paris, Bonn, Argonne-V14, and Reid NN potentials to include the coupling to the πNN production channel. The pion production through the Δ excitation is described by a πN⇆Δ vertex and a $V_{\mathrm{NN}\mathit{\leftrightarrows }\mathrm{N}\mathit{\Delta }}$ transition potential, while the production through nonresonant πN interactions is described by a transition operator $F_{\pi \mathrm{NN}\mathit{\leftrightarrows }\mathrm{NN}}$. It is found that none of the constructed models can accurately reproduce all NN and πd elastic scattering data, in particularly the data of polarization observables. Our results indicate that either the conventional phenomenological parametrizations of baryon-baryon interaction at short distances are not valid in the intermediate energy region, or some genuine quark dynamics has already been revealed in the πNN data.