Protons scattered inelastically from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ were detected at laboratory angles between 6° and 13° in coincidence with $\gamma$ rays from deexcitation of the $1^{+} T=1\mathrm{}$ state in the recoil nucleus. Coincident cross sections for $\gamma$ rays emitted normal to the reaction plane and angular correlations for $\gamma$ rays emitted in the proton scattering plane at angles between 90° and 270° are presented and compared with predictions from both nonrelativistic and relativistic models of proton-nucleus scattering calculated in the impulse approximation. These data display a clear preference for the relativistic-model prediction.

Evidence is presented for the occurrence of superdeformation in $\mathrm{sd}$-shell nuclei. Neutron-proton coincidence spectra from the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=24\mathrm{}$ MeV were measured. The neutron evaporation spectrum at low energies directly reflects the large deformation of the emitting system, extending to states above the yrast line. The strong energy dependence of the effect implies that the compound nucleus undergoes a rapid change from nearly spherical to superdeformed shapes over a narrow range of excitation energy. The transition to a fissioning system should be observable.

We have begun a program to measure dielectron production in $p$-nucleus and nucleus-nucleus collisions at the LBL Bevalac. Results are presented for the reaction $p+\mathrm{Be}$ at 4.9 GeV. For the first time, direct dilepton production is observed below 10 GeV incident energy. The cross sections are discussed and compared to previous data at higher energies. The observation of a structure at a mass of about 275 MeV suggests that pion annihilation may be the dominant production mechanism in this mass range.

We present results of our systematic studies of charged-shower-particle multiplicities and their dependence on pseudorapidity intervals for nearly central events produced by ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ at 200 GeV/nucleon and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at 200 and 60 GeV/nucleon in nuclear emulsion. An increase in the particle density with the increase of particle energy and mass is observed. We find an energy-independent linear relation between the maximum particle density (in a given pseudorapidity interval) and shower-particle multiplicity.

Modified Faddeev-type three-nucleon equations that also include the Coulomb potential between the two protons are solved in momentum space. With a separable representation of the Paris potential for the $N-N {}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$, the coupled ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$, and the $P$ states, we have calculated for the first time $p-d$ polarization observables. Our $p-d$ results at $E_p=2.5\mathrm{}$ MeV are compatible with the measured $p-d$ data and demonstrate that a proper treatment of the $p-d$ Coulomb corrections is required.

The isoscalar monopole and quadrupole giant multipole resonances of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been studied in the excitation region of 9 to 16 MeV by coincident electron scattering. Concentrations of strength have been found at 10.4 and 14.2 MeV, in reasonable agreement with the predictions of mean-field theory. The measurements reported are the first nuclear-structure investigation carried out by use of the ($e,e^{\prime }n$) reaction.

From the interactions of a deuteron beam in a liquid-hydrogen target at energies near the $d+p\to {}_{}{}^3{}_{}{}^{}\mathrm{He}+\eta$ threshold, $\eta$ events were selected on the basis of the momentum-analyzed ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ with a background of less than 2%. This opens the way to a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-tagged $\eta$ beam at Saturne, with a possible flux of ${10}^4$-${10}^5$ $\eta \text{'}\mathrm{s}$ per pulse. The present data allow an evaluation of the cross section down to less than 0.5 MeV above threshold. The deuteron tensor analyzing power $t_{20}$ has also been measured: The small negative value found at threshold (-0.15 ± 0.05) seems incompatible with models based on one-pion exchange.

The first triple-coincidence data resulting from pion absorption in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are reported. The existence of a three-nucleon absorption component in the four-nucleon channel is established. A four-nucleon phase-space-like contribution and nucleon-nucleon final-state interactions are also identified.

In a spectroscopic study of the backward-angle yield from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+ ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ at 3-4 times the Coulomb barrier, we find a strong preference for natural parity transitions in the excitation of close-to-yrast rotational bands. This selectivity is in strong quantitative disagreement with Hauser-Feshbach calculations for a compound-nuclear reaction and provides evidence for the conservation of the dinuclear parentage.

Cross sections for 180° inelastic electron scattering from deuterium were measured from breakup threshold to beyond the quasielastic peak for incident-beam energies of 0.843, 1.020, 1.189, and 1.281 GeV, corresponding to $0.75\le Q^2\le 2.57$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The data are in reasonable agreement with nonrelativistic models that include final-state interactions and meson-exchange currents. The scaling function $F\left(y\right)\mathrm{}$ for these data is generally in agreement with $F\left(y\right)\mathrm{}$ for forward-angle data at the same $Q^2$. Values of $G_M^n$ determined from the data are in good agreement with results from previous experiments.

Differential cross sections for the photodisintegration of deuterium between 6 and 9 MeV are reported. Highly monochromatic photon sources from the ($n,\gamma$) reaction and a high-resolution neutron spectrometer were employed to measure the neutron yield between 30° and 155°. The results were found to be in good agreement with the standard theory.

Calculations have been performed for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}(\gamma ,p)$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\gamma ,p)$ reactions at intermediate energies. Both the direct (single-particle) and pion-exchange-current mechanisms have been included using relativistic forms of the nucleon current operator and four-component nucleon wave functions.

We analyze the process of fragmentation in heavy-ion interactions from the viewpoint of growth of instabilities in hot, expanding nuclear matter. The growth rates of modes in a medium unstable to small density perturbations of finite wavelengths are calculated from a kinetic equation. This enables us to treat the case where the nucleon mean free path is comparable to or greater than the wavelength of the fluctuation, and the temperature is arbitrary. We estimate for hot nuclear matter the initial conditions which, after expansion, will result in fragmentation, evaporation, or vaporization.

Cross sections and a complete set of seven independent spin observables have been measured for inclusive quasielastic scattering of 290-MeV protons from ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ at a quasifree momentum transfer of 1.36 ${\mathrm{fm}}^{-1\mathrm{}}$ and energy transfers varying from 0-90 MeV. Comparison of the results with relativistic and nonrelativistic impulse-approximation models shows that Fermi-motion averaging, a realistic nuclear response function, and medium modifications of the $\mathrm{NN}$ interaction are essential ingredients of a successful theory.

${\chi }^2$ mappings in the necessary, but generally unsearched, sixth parameter of the ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}F_2^{}{}_{}{}^{} N-N$ partial wave around 1 GeV reveal a strong preference for single-channel dominance of the inelasticity. This is consistent with the constraint imposed by fixing the sixth parameter in the VPI analyses but it is contrary to the hidden constraint imposed upon all other analyses of nucleon-nucleon elastic scattering.

We report the first observation of a double isovector giant dipole state in nuclei (i.e., an isovector giant dipole resonance built on another giant dipole). Two new resonances were observed in (${\pi }^{+},{\pi }^{-}$) double charge exchange (at $T_{\pi }=292\mathrm{}$ MeV) on ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{S}$ at excitation energies of 24.7 and 28.7 MeV. The energy centroid is very close to the energy at which the double dipole ($J^{\pi }=0^{+},2^{+};T=2\mathrm{}$) state is expected to appear. The angular distributions for the resonances have a clear quadrupole shape. The measured cross sections and the angular distribution agree well with a simple sequential two-step calculation in which single charge exchange through the giant dipole resonance to the double dipole is evaluated.

Electroproduction of the $\Delta$ isobar in C and Fe has been studied for incident electrons with energies between 0.6 and 1.6 GeV. A longitudinal-transverse decomposition of the inclusive cross section has been made for $q_{\mu }^2=0.1\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The residual longitudinal cross sections measured do not provide the additional strength needed above the quasifree region to satisfy the Coulomb sum rule. The transverse cross sections are in good agreement with data from photoabsorption.

Complex fragments of nuclear charge $Z$ from 4 to 13 were measured at five laboratory angles by use of surface-barrier-detector telescopes. Coincident $\gamma$ rays were measured in a $4\pi$ geometry using 64 NaI detectors. Kinematical analysis of the fragments revealed that those of $Z$ between 4 and 9 are consistent with the decay of a compound nucleus formed in a complete fusion reaction. $\gamma$ rays of excited states of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ were measured and effective temperatures of about 2 MeV were extracted. Hauser-Feshbach calculations reproduce the measured cross sections and the effective temperatures very well.

The effect of quantal and thermal quadrupole shape fluctuations in the giant dipole response function of hot nuclei at high spin is studied within the Landau theory of phase transitions. The effects are found to be important in the relation of the nuclear shape to the experimental findings, and in the identification of shape phase transitions.

With a residual interaction consisting of density-independent two- and three-body parts, we obtain within Hartee-Fock-Bogolyubov theory at the same time good results on the odd-even staggering of charge radii and on trends of the pairing energies. We present results for Sn and some isotopic chains in the Ba region.