The reaction ${}_{}{}^{78}{}_{}{}^{}\mathrm{Se}$(t,p${)}^{80}$Se has been investigated with 17-MeV tritons. Twenty-eight levels of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Se}$ were observed up to an excitation energy of 5.2 MeV, and angular distributions have been extracted for twenty-two of them. Comparisons are made with distorted-wave Born-approximation calculations, allowing $J^{\pi }$ assignments to be made for most of the levels observed.

Neutron differential-elastic-scattering cross sections of yttrium were measured from 4 to 10 MeV, at energy intervals of approximately 500 keV, and at 20 or more angles distributed between 20° and 160°. The results were combined with data previously reported from this laboratory to obtain a detailed data base extending from 1.5 to 10.0 MeV. These data were interpreted using a spherical optical-statistical model, including the surface-peaked real potential predicted by the use of dispersion relations. The volume integral of the real potential, $J_V$, was found to decrease linearly with energy, and that energy dependence was accounted for using the dispersion relationship linking the real and imaginary potentials. Thus, in the energy range of the present measurements, the neutron interaction with ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ does not display a Fermi-surface anomaly of the nature reported in the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ region. On the other hand, the energy dependence of $J_V$ needed to give the correct binding energies for the single-particle and single-hole states did tend toward constant values with decreasing energy, as expected, and perhaps even a decrease is suggested by some of the hole states.

Cross sections for the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(p,2p) reactions at 101.3 and 76.1 MeV and the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(p,2p) reaction at 101.3 MeV have been measured and analyzed using distorted-wave impulse approximation calculations. The sensitivity to the choice of distortion parameters, nonlocality corrections, and spin-orbit terms in the optical potentials have been studied. For the region of phase space studied, the factorization approximation is found to be valid even at energies as low as 76.1 MeV. Extracted spectroscopic factors are compatible with shell model estimates.

The resonances at $E_{\mathrm{p}=3774\mathrm{}}$ and 3794 keV in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ are identified as fragments of the $d_{5/2}$ isobaric analog resonance from ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$(p,γ) and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$(p,p’γ) reactions. Gamma-decay schemes and angular distributions have been studied. From angular distributions and symmetry potential considerations, the level at 4675 keV in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ is considered to be the antianalog state. The M1 transition strength of the analog-antianalog state has been measured and is compared with theoretical predictions. Additional information on the M1 strength systematics in the isovectorial ${\mathrm{}(5/2)\mathrm{}}^{+}$→${\mathrm{}(5/2)\mathrm{}}^{+}$ transitions in the f-p shell nuclei is provided.

The ${}_{}{}^{97}{}_{}{}^{}\mathrm{Ru}$ and ${}_{}{}^{103}{}_{}{}^{}\mathrm{Ru}$ nuclei have been studied via in-beam gamma ray spectroscopy through the ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$(α,n${)}^{97}$Ru, ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$${(}^6$Li,p2n${)}^{97}$Ru, and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$(α,n${)}^{103}$Ru reactions. Partial levels schemes can be proposed from γ-γ coincidence data, whereas excitation function and angular distribution measurements were used to determine the spins of several excited levels. The results are compared to previous work carried out on these nuclei.

We analyze completely exclusive 1 GeV/nucleon gold-emulsion reaction data with special emphasis on quantities which may help to settle the unsolved problem of which reaction mechanism produces the multifragmentation of heavy nuclei. We present results on correlations between target fragments and projectile fragments and among projectile fragments. In particular, we present for the first time the evolution of the mass yield distribution with the violence of the collisions which is characterized by the number of Z=1 particles. We find that events producing Z=2 particles have a different signature than those producing medium mass fragments. This shows that the agreement of the data with theories describing the inclusive mass yield by a single process—like a liquid gas phase transition—is accidental.

The reaction ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${(}^6$Li,t${)}^{12}$C was studied at 32 MeV. Selective population of states was observed up to the 14.1 MeV state in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The high probability for three or more body processes resulted in a large continuum yield which prevented the observation of the population of states in the 17–22 MeV excitation region of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. Hauser-Feshbach calculations show that the statistical compound nucleus contribution to the cross section is small. The experimental angular distributions are well reproduced by distorted-wave Born approximation calculations. The extracted relative spectroscopic strengths are in good agreement with theoretical values. The T=1 15.1 and 16.1 MeV states were not observed. A measurement of the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${(}^6$Li${,}^3$He${)}^{12}$B cross sections to their analog states shows that these states would have a peak height of only 10% of the continuum yield, making it difficult to determine if these states are populated in the present reaction.

We study the electromagnetic excitation of high-lying nuclear states by means of peripheral relativistic heavy ion collisions. The present experimental evidence for the excitation of E1 and E2 giant resonances is discussed theoretically. The multiphonon giant dipole resonance excitation is explored. Absolute values of cross sections for N-phonon excitations are given using the harmonic oscillator model. The role of the damping of the giant resonance states is investigated.

The ground state Q value of the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^7$Li, ${}_{}{}^8{}_{}{}^{}\mathrm{He}$${)}^{57}$Cu has been measured and found to be -29.613(17) MeV. This corresponds to a ${}_{}{}^{57}{}_{}{}^{}\mathrm{Cu}$ atomic mass excess of -47.303(15) MeV. At a beam energy of 76.5 MeV and a scattering angle of 7°, the observed cross section was 17 nb/sr. The implications of these results are discussed.

We report the results of three-pion interferometry for two streamer chamber data samples: 1.8 GeV/nucleon Ar on Pb and 1.5 GeV/nucleon Ar on KCl. The fitted pion source parameters are consistent with previously reported results of two-pion interferometry. The effect of three-pion interference on the pion source parameters obtained from two-pion interferometry is also studied. The distortion becomes a serious problem in the data analysis only when the pion source has a small radius and low temperature.

The reactions ${}_{}{}^{40}{}_{}{}^{}$Ar${+\mathrm{}}^{27}$Al, ${}_{}{}^{45}{}_{}{}^{}$Sc, ${}_{}{}^{58}{}_{}{}^{}$Ni, ${}_{}{}^{90}{}_{}{}^{}$Zr are studied at 600 MeV bombarding energy. The experiments employ several large-area detectors of different kinds to identify heavy fragments and measure their multiplicity. Two- and three-fragment channels are observed in all reactions and their cross sections are determined. The existence of four-fragment channels is suggested by the experiment; their contribution is, however, too weak for a detailed analysis. In addition to the multifragmentation processes, the emission of light particles is also observed, the average charge of all emitted particles being slightly smaller than expected from experiments at lower energies. The predominant source of light particles is the evaporation from hot fragments. In the light systems the existence of three fragments is ascribed to a fast disintegration process, whereas in the heaviest system a major part of such channels could also arise from a sequential fission process.

We have studied ${}_{}{}^{14}{}_{}{}^{}$N${+\mathrm{}}^{165}$Ho and ${}_{}{}^{14}{}_{}{}^{}$N+Ni collisions at 35 MeV/nucleon by detecting neutrons at ten angles from 10° to 160° in coincidence with light fragments at six angles between 7° and 30°. For a given fragment, the seven spectra of coincident neutrons whose angles are not near the fragment angle were fitted with two moving, thermal sources. One source is a slowly-moving, targetlike source; the other is a faster (approximately half-beam-velocity), hotter source. The latter source, an intermediate-rapidity source, reproduces a left-right asymmetry in which the fragment-neutron cross sections are larger for emission to opposite sides of the beam axis than for emission to the same side. The temperature of the targetlike source is about 3.5 MeV with the Ni target and about 2.5 MeV with the Ho target. The corresponding values for the intermediate-rapidity source are 10 and 8.5 MeV. These source temperatures are approximately independent of fragment angle, but the measured neutron multiplicities increase with fragment angle. For the targetlike source the largest multiplicities, 1.6 for Ni and 9 for Ho, are about (3/4) the values computed with a statistical code. The multiplicities of the intermediate-rapidity source are about (1/4) the multiplicities of the targetlike source. The necessity for an intermediate-rapidity source is also demonstrated in terms of ‘‘missing momentum’’ in the final state of an assumed two-body, ${}_{}{}^{14}{}_{}{}^{}$N+target inelastic collision. The mass number of this source is estimated in peripheral collisions and in central collisions. The approximate independence of source parameters on fragment angle may indicate that the neutrons and the fragments are emitted at different times during the reaction. The neutron multiplicities of the two sources have a parallel upward trend with fragment angle, indicating that the two sources may be correlated. We speculate that a small, hot source evolves into the cooler, large targetlike source.

Coulomb excitation experiments have been performed on ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ targets with 370 and 450 MeV ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ projectiles. The deduced experimental level scheme exhibits 11 band structures developed up to high spins. A rotor-plus-quasiparticle microscopic approach, free of any ad hoc parameter adjustment, has been applied to this nucleus yielding a very good reproduction of band-head energies, moments of inertia, multipole moments, and transition probabilities, which assesses the relevance of the underlying Hartree-Fock plus BCS mean field description.

Inclusive cross sections for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{40}$Ca reaction leading to fission-like fragments with mass 20≤$A_{\mathrm{fragment}\mathrm{\le }}$28, and for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{44}$Ca reaction with 20≤$A_{\mathrm{fragment}\mathrm{\le }}$30, have been determined by measurements at seven energies with 69.3≤$E_{\mathrm{lab}{(\mathrm{}}^{16}}$O)≤87.3 MeV and for 30°≤${\mathrm{theta}}_{\mathrm{lab}\mathrm{\le }60\mathrm{°}}$. The evaporation-residue cross sections were also measured over a limited angular range at the same energies to search for any gross difference between these cross sections for the two systems. No difference was detected outside the experimental uncertainties. The resulting energy spectra and mass distributions for the fission-like yields are shown to be consistent with a fusion-fission reaction mechanism. Although it was not possible to determine the total fission-like cross sections since the apparent mass range of the fission-like yields was greater than that covered by the experiment, the magnitude and energy dependence of the observed fission-like cross sections, as compared to the evaporation-residue cross sections, are also found to be consistent with a fusion-fission mechanism.

The (${\pi }^{+}$,2p) and (${\pi }^{\pm }$, pn) reactions were studied by coincidence detection of the outgoing nucleons on C, Fe, and Bi at 165 and 245 MeV and on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ at 165 MeV. The quasideuteron component is identified and found to account for only about 10% of the absorption cross section for carbon down to about 2% for bismuth. With corrections for the final-state interaction of outgoing nucleons it amounts to at most 40%. The data indicate that quasideuteron absorption following pion scattering is not likely. The absorption on T=1 nucleon pairs is about 4% of that on quasideuterons.

Measurements of ${\pi }^{\pm }$p elastic differential cross sections have been made at seven incident pion energies from 66.8 to 138.8 MeV. These measurements have statistical accuracy of 1.5–3.3?for ${\pi }^{+}$ and 2.7–19.0?for ${\pi }^{\mathrm{-}}$. The absolute normalization uncertainties are 1.2–2.5?for ${\pi }^{+}$ and 1.2–3.2?for ${\pi }^{\mathrm{-}}$. Extensive tests were made to ensure that systematic errors were properly evaluated.

A recently performed high accuracy measurement indicates the existence of a spin and isospin nonconserving force in neutron-proton scattering. One origin of this effect can be the influence of the up and down quark mass difference on the one gluon exchange spin-orbit force. We include this effect in a resonating group calculation, and find that its contribution is very small compared to that conventional meson-exchange forces.

We investigate pion production via nucleon-nucleon scattering, i.e., N+N→N+N+π, assuming that pion emission takes place effectively at the quark level and that quark-quark interactions are described to a reasonable approximation by one-gluon exchange plus effective one-pion exchange. The six-quark wave function is totally antisymmetrized. Consequently, reaction mechanisms may be grouped into several categories: (1) one-nucleon mechanism or the nucleon-only impulse approximation, (2) two-nucleon mechanisms or meson-exchange currents, and (3) reaction mechanisms involving quark interchange. Applying the formalism to the reactions p+p→d+${\pi }^{+}$ and n+p→p+p+${\pi }^{\mathrm{-}}$, we find that, for a nucleon radius of greater than 0.8 fm (as measured in the MIT bag model), reaction mechanisms involving quark interchange may be as important as the conventional one-nucleon or two-nucleon reaction mechanisms even near the pion production threshold. This specific result provides a quantitative support of the conclusion reached by Miller and Kisslinger in the hybrid quark-baryon model concerning the necessity of incorporating quark effects in describing pion production or absorption reactions.

Antiproton-proton annihilation leading to ${\mathrm{K}}^{\mathrm{-}}$${\mathrm{K}}^{+}$, ${\mathrm{K}}_{\mathrm{S}}$${\mathrm{K}}_{\mathrm{S}}$, and ${\mathrm{K}}_{\mathrm{S}}$${\mathrm{K}}_{\mathrm{L}}$ is analyzed using a baryon exchange model with Λ and Σ exchange, employing simple eikonal damping in the initial and final states. The initial state interaction is constrained to fit the p¯p elastic scattering and polarization data, while the strength and range of the K¯K interaction are varied to fit the p¯p→${\mathrm{K}}^{\mathrm{-}}$${\mathrm{K}}^{+}$ differential cross section data. Although the magnitude can be obtained in such a model, the cross sections fall off monotonically with angle. The structures in σ(theta) data force incorporation of resonances like the ξ, excited ρ, and ε. The ${\mathrm{K}}^{\mathrm{-}}$${\mathrm{K}}^{+}$ data are analyzed using a simple Breit-Wigner parametrization of resonances in conjunction with the background. The ${\mathrm{K}}_{\mathrm{S}}$${\mathrm{K}}_{\mathrm{S}}$ and ${\mathrm{K}}_{\mathrm{S}}$${\mathrm{K}}_{\mathrm{L}}$ cross sections are then predicted. Complete measurements of cross sections and analyzing power for ${\mathrm{K}}^{\mathrm{-}}$${\mathrm{K}}^{+}$, ${\mathrm{K}}_{\mathrm{S}}$${\mathrm{K}}_{\mathrm{S}}$, ${\mathrm{K}}_{\mathrm{S}}$${\mathrm{K}}_{\mathrm{L}}$, ${\pi }^{\mathrm{-}}$${\pi }^{+}$, and ${\pi }^0$${\pi }^0$ are needed to understand the role of the resonances in the M¯M system.

Nuclear γ rays in coincidence with outgoing pions or protons following single-nucleon removal from ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ by 200-MeV ${\pi }^{+}$ have been detected with Ge(Li) detectors. Differential cross sections are reported for γ rays from the first excited mirror states of ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$ in coincidence with positive pions or protons detected in particle telescopes at 30°, 60°, 90°, 120°, and 150°; angle-integrated absolute cross sections and cross section ratios σ${(\mathrm{}}^{23}$Mg)/σ${(\mathrm{}}^{23}$Na) are calculated. These results are compared with the predictions of a Pauli-blocked plane-wave impulse approximation and the intranuclear cascade and nucleon charge exchange reaction models. The plane-wave impulse approximation and the intranuclear cascade calculations generally agree with the angular dependence of the experimental results but not the absolute magnitude. The nucleon charge exchange calculation does not reproduce the observed cross section charge ratios.