Spectra of energetic protons and deuterons emitted following negative muon capture from rest in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ have been measured for the first time. Significant capture strength is observed at high energy transfers (${\mathit{m}}_{\mathrm{\mu }}$-${\mathit{E}}_{\nu }$>60 MeV) for the two-body and three-body breakup channels, indicative of the importance of nucleon-nucleon correlations and meson exchange currents in the capture process. A simple plane wave impulse approximation calculation reproduces the proton spectrum reasonably well, but underpredicts the deuteron rate at the highest energies by a large factor.

The statistical decay of an equilibrated hot nucleus is modeled by sampling the microcanonical phase space for nuclear fragmentation. It is shown to reproduce the measured fluctuations and correlations (intermittency) in data for 1 GeV/nucleon ${}_{79}{}^{197}{}_{}{}^{}\mathrm{Au}$ on emulsion. Within our model multifragmentation is linked to the nuclear liquid-to-gas phase transition. The model is used to realistically study the conditions leading to the phenomenon of intermittency in critical heavy-ion reactions.

Strong direct processes were observed for elastic breakup in 54-MeV ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{12}$C ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ reactions. In the case of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, the observed ${}_{}{}^7{}_{}{}^{}\mathrm{\alpha }$+t direct-breakup yield was significantly larger than predicted by a Coulomb-breakup calculation, indicating the importance of the nuclear field. For ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, final-state interactions produced a strong distortion in the fragment energy spectra, as well as a modulation of the coincidence efficiency for different detector geometries. Such Coulomb effects are found to severely complicate the extraction of radiative-capture cross sections from direct-breakup data.

Spectroscopy of superdeformed nuclear states opens up an exciting possibility to probe new properties of the nuclear mean field. In particular, the unusually deformed atomic nucleus can serve as a microscopic laboratory of quantum-mechanical symmetries of a three-dimensional harmonic oscillator. The quantum numbers and coupling schemes characteristic of weakly deformed systems are expected to be modified in the superdeformed world. New classification schemes can be directly related to certain geometrical properties of the nuclear shape.

In order to investigate whether entrance-channel effects influence the production of superdeformed nuclei, we have measured the yield of the yrast superdeformed band in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ populated via nearly mass-symmetric ${(}^{82}$Se${+}^{74}$Ge) and mass-asymmetric ${(}^{48}$Ca${+}^{108}$Pd, ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$${+}^{120}$Sn) fusion reactions leading to the same compound nucleus at similar excitation energies and angular momenta. Large differences in the relative intensity of the band compared with the total yield of the nucleus are observed in the various reactions. This effect indicates that the competition between fission and neutron evaporation is affected by the mode of formation of the fusing system.

The light-cone nucleon momentum distributions obtained from nonrelativistic spectral functions or given by nuclear-binding/pion models are often used to analyze high-${\mathit{Q}}^2$ quasielastic and deep-inelastic (e,e’) reactions. We demonstrate that in such models the presence of non-nucleonic components causes the scattering from forward and backward moving target protons to be significantly different. Other models do not have this property. The sensitivity of current (e,e’p) and (p,pp) color transparency experiments is sufficient to observe these differences.

We studied ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ ${\mathrm{\beta }}^{+}$ decays using a mass separated ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ beam and a proton telescope with 16-keV resolution. Delayed p’s were detected in coincidence with γ’s to identify p decays of ${}_{}{}^{37}{}_{}{}^{}\mathrm{K}$ daughter levels to excited states of ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$. We observed 43 previously undetected proton groups, yielding an integrated B(GT) twice as large as that observed previously. Although our result increases the efficiency of the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$ detector for counting solar ν’s by 6%, its main effect is to reduce uncertainties in this efficiency arising from discrepancies between previous ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ β decay and ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) results.

The measured Gamow-Teller strength in ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ ${\mathrm{\beta }}^{+}$ decay, which has an unusually high energy release, differs significantly from shell-model predictions and also from the analogous strength inferred from the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) reaction. This calls into question the claim, based primarily on shell-model analyses of low-energy-release β-decay rates and (p,n) cross sections, that ${\mathit{g}}_{\mathit{A}}$ is significantly renormalized in complex nuclei.

Co and Fe isotopes have been identified in thermal-neutron-induced fission of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$. The yields of the very neutron-rich isotopes ${}_{}{}^{69}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{68}{}_{}{}^{}\mathrm{Co}$, and ${}_{}{}^{68}{}_{}{}^{}\mathrm{Fe}$ were measured and their β-decay half-lives were obtained from time correlations between detection of the selected isotopes and of the β particles from their decay.

It is shown that the recently reported strong enhancement of the axial-charge matrix element in first-forbidden β decay in heavy nuclei (A=205–212) can be simply explained in terms of an effective Lagrangian that incorporates approximate chiral and scale invariances of QCD. We suggest this as an evidence for the scaling property of hadrons in dense medium as predicted by effective chiral Lagrangians that are consistent with the symmetries of QCD.

We report the observation of a large asymmetry in the elastic scattering of 100 MeV ${\mathrm{\pi }}^{+}$ from a polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ target. Measurements have been made at laboratory angles of 60°, 80°, and 100°, with the largest value ${\mathit{A}}_{\mathit{y}}$=0.89±0.12 occurring at 80°, near a cross-section minimum. This asymmetry is the largest observed to date in pion scattering from a spin-1/2 nucleus. The ${\mathit{A}}_{\mathit{y}}$ data are qualitatively reproduced by a schematic model; however, agreement with the data is significantly improved when realistic three-body Faddeev wave functions and a full nonlocal distorted-wave impulse approximation reaction model are used.

Experimental evidence testifying to the existence of a limiting temperature for the observation of gamma decay from the giant dipole resonance in hot nuclei is interpreted as indicating a remarkable constancy with temperature of the width with which the giant resonance couples to the compound nucleus.

Exclusive measurements of two- and three-body events were performed for the system ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$${+}^{100}$Mo at 19.1 MeV/nucleon. Most ternary events are consistent with sequential processes in which one of the two deep-inelastic fragments fissions. For such events large differences are found between the fission probabilities of projectilelike and targetlike fragments of a given mass, this probability being larger for the nucleus which gained nucleons. This behavior demonstrates that there is a lack of equilibrium at the end of the deep-inelastic collision.

The commonly held view that fusion excitation functions are featureless and do not provide a good test of models is challenged by high-precision measurements for the reaction ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$${+}^{16}$O. The data yield a well-defined distribution of barrier heights using a recently proposed, novel analysis technique. The measured distribution is that expected from the quadrupole deformation of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ and models using significantly different distributions cannot reproduce the measured excitation functions.

The half-life for the decay of ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ to ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$ has been measured to be (2.0±0.6)×${10}^{21}$ yr by chemically isolating and measuring from the resultant alpha particles the amount of plutonium that had accumulated in 35 yr from 8.4 Kg of purified uranyl nitrate. Other sources of ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$ have been studied and found negligible.

Fluctuations in the wave functions of hadrons in inelastic interactions with nuclei are important for nuclear collisions at high energy, where the internal hadronic configurations can be considered frozen. Modeling fluctuations by a distribution of cross sections, we calculate their effect on multiplicity and transverse energy production in central high-energy nuclear collisions, and find that they can account for the large fluctuations found experimentally.

The transitional nucleus ${}_{}{}^{86}{}_{}{}^{}\mathrm{Zr}$ has been studied by the ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$${(}^{30}$Si,2p2n) reaction, with γ-γ coincidence, angular correlation, Doppler-shift-attenuation and measurements. Band structures exhibiting strongly staggered M1 transition rates were found at high spins, with large B(M1) values but no significant E2 collectivity. The unusual behavior of this nucleus is interpreted within the framework of an interacting boson model incorporating two broken boson pairs. This new model for high-spin states is seen to be remarkably successful in describing the electromagnetic decay properties in the four-quasiparticle regime.

The disappearance of transverse collective flow for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{27}$Al collisions is studied with an improved Boltzmann-Uehling-Uhlenbeck equation. For collisions at impact parameters less than 3 fm, the predicted energy of balance, ${\mathit{E}}_{\mathrm{bal}}$, is very sensitive to the in-medium nucleon-nucleon cross section, but insensitive to the equation of state. At larger impact-parameter collisions, the sensitivities to both the in-medium nucleon-nucleon cross section and the equation of state at subnuclear density becomes comparable. Comparisions with experimental data indicate an in-medium nucleon-nucleon cross section in the range of 25–45 mb.

The (α+d) breakup of 60 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ scattered from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ has been measured inside the grazing angle for c.m. energies of the fragments between 100 keV and 1.5 MeV. We find the integrated cross sections to be in agreement with Coulomb excitation theory, but the angular correlations of nonresonant breakup exhibit significant deviations from this theory. This shows that the measured breakup cross section cannot be related by first-order Coulomb excitation theory to the astrophysically relevant ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(d,γ${)}^6$Li capture reaction.

We study supersymmetric quantum mechanics with particular emphasis on factorization as a key to understanding the recently discovered isospectral γ ray cascades seen in neighboring superdeformed nuclei. Explicit realization of the general algebraic approach leads to state doubling in the odd-A nucleus.