An energy-dependent one-dimensional potential barrier for heavy-ion fusion reactions is shown to be consistent with the full dynamical coupled-channel calculation, provided the potential is written in terms of the kinetic energy ɛ in the relative-separation coordinate at the fusion barrier. It is also shown that earlier conclusions about the inadequacy of the energy-dependent barrier-penetration model is a direct consequence of expressing the energy dependence as a function of the center-of-mass bombarding energy ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$.

The orthonormal-correlated-states method is used to study the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(e,e’p${)}^3$H reaction. The effects of short-range correlations, orthogonality corrections, p${+}^3$H interaction in the final states, and two-body charge and current operators bring the theoretical predictions into fair agreement with the NIKHEF and Saclay data.

The influence of the color van der Waals force in the elastic scattering of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at sub-barrier energies is studied. The conspicuous changes in the Mott oscillation found here are suggested as a possible experimental test.

The cross sections for massive residues from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${+}^{40}$Ca and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{27}$Al collisions were calculated with an improved Boltzmann-Uehling-Uhlenbeck equation. The calculated residue cross sections decrease with incident energy, an effect which does not appear related to the residue excitation energy. Larger residue cross sections result from calculations with larger in-medium nucleon-nucleon cross sections or with equations of state which are less attractive at subnuclear density. This dual sensitivity may be eliminated by measurements of observables associated with the coincident light particles.

Breakup of 63-MeV and 42-MeV ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ near the α-t threshold is examined from the astrophysical point of view. A new approach is made to extract indirectly astrophysical S factors. The S factors are compared with those deduced from radiative-capture measurements. It is shown that the energy dependence favors the recent capture data of Schröder et al.

It is demonstrated that existing np→dX data show a strong signal for the two-body reaction np→dη near its threshold. The cross sectio n is much larger than that for the analogous ${\mathrm{\pi }}^0$ threshold production, but is in accord with a model where production is dominated by the ${\mathit{S}}_{11}$ ${\mathit{N}}^{\mathrm{*}}$(1535) resonance. The Abashian-Both-Crowe enhancement ${\mathit{X}}_{\mathrm{ABC}}$ is a prominent feature of the data. It is shown that the np→${\mathit{dX}}_{\mathrm{ABC}}$ process at 1.9 GeV/c, which contains most of the 2π production, is almost isotropic, in constrast to theoretical models.

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nuclei. Our result is ${\mathit{A}}_{\mathrm{expt}}$=0.60±0.14±0.02 ppm, where the first error is statistical and the second is systematic. With a beam polarization of 0.37, we compute the isoscalar vector hadronic coupling constant γ̃ to be 0.136±0.032±0.009. The standard model predicts γ̃=0.155 at the tree level, in agreement with our data.

We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ gas target. This measurement represents the first demonstration of a new method for studying electromagnetic nuclear structure: the scattering of polarized electrons from a polarized nuclear target. The measured asymmetry is in good agreement with a Faddeev calculation and supports the picture of spin-dependent quasielastic scattering from polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ as predominantly scattering from a polarized neutron.

Inelastic electron scattering is used to identify nine stretched isovector [${\mathit{T}}_{>}$ (${\mathit{T}}_0$→${\mathit{T}}_0$+1) M6 transitions in ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ (${\mathit{T}}_0$=0) which exhaust (77±17)% of the extreme single-particle-hole-model sum rule. This is the first time that several prominent ${\mathit{T}}_{>}$ electromagnetic stretched transitions have been observed in a self-conjugate nucleus and the first time that such a large fraction of the sum rule has been observed. These effects are primarily due to the presence of spectator nucleons in the 2${\mathit{s}}_{1/2}$ orbit, as substantiated by shell-model calculations.

Cross sections at 0° for the pure Fermi ($0^{+}$, 2.31, MeV) and Gamow-Teller ($1^{+}$, 3.95 MeV) states in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(p,n${)}^{14}$N reaction have been measured at ${\mathit{E}}_{\mathit{p}}$=494, 644, and 795 MeV using the LAMPF neutron time-of-flight facility with a new 617-m neutron flight path. The measured cross sections per unit transition strength, σ^, provide a measure of the isovector spin-flip and non-spin-flip central components of the effective nucleon-nucleon interaction. Cross sections and the ratio ${\mathit{R}}^2$=σ${\mathrm{^}}_{\mathrm{GT}}$/σ${\mathrm{^}}_{\mathrm{F}}$ are compared to lower-energy measurements and to calculations using a free NN t matrix.

S+Au interactions at 200A GeV were observed using emulsion chambers, permitting measurement of pseudorapidities in the central region with precision ∼0.01 unit. Scaled-factorial-moment analyses are extended to bin sizes smaller than those accessible to other fixed-target experimental techniques. For a sample of 151 central collisions, moments are calculated using both ‘‘horizontal’’ and ‘‘vertical’’ analysis techniques. While the moments are found to rise (in a log-log plot) with decreasing pseudorapidity bin size δη, their slopes roll off to approximately zero for δη<0.1.

A sensitive study of the decay of the deformation-aligned K=14, 4-μs isomer in ${}_{}{}^{174}{}_{}{}^{}\mathrm{Hf}$ has revealed a multitude of the K-forbidden branches to the ground-state rotational band and other low-K bands, in competition with the known decays to high-K bands. The isomeric transitions have consistently low hindrance factors. These anomalous findings in an axially symmetric deformed nucleus severely test our understanding of the K-selection rule. The isomeric decay to an I=12 rotation-aligned state, and its mixing with the I=12 yrast state, provide a partial explanation.

The reactions ${\mathrm{\pi }}^{\mathrm{-}}$d→${\mathrm{\pi }}^0$X and ${\mathrm{\pi }}^{+}$d→${\mathrm{\pi }}^{+}$X are calculated within a relativistic three-body model and compared with recent data at 164.1 and 96.5 MeV, respectively. Contrary to expectations based on the impulse approximation, the differential cross sections of both reactions exhibit a strong suppression in the forward direction. It is shown that this suppression is due in the first case to the action of the Pauli principle on the two final neutrons, and in the second case to the orthogonality between the initial deuteron and final neutron-proton wave functions. The results of the full model agree well with the available differential cross sections at the two energies.

Coincident neutrons from the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$${+}^{26}$Mg${\to }^{44}$Ca (${\mathit{E}}_{\mathit{x}}$=60 and 71 MeV) compound-nuclear reaction show an anticorrelation at small relative momentum, giving evidence for quantum-statistical interference in analogy to the optical Hanbury-Brown and Twiss effect. An average decay width of 60 keV is extracted from the measured energy correlations. The deduced extension of the neutron wave packets exceeds by far the nn scattering length, in accordance with the observed insignificance of the attractive nn final-state interaction.

Nine superdeformed bands in several nuclei of the mass-190 region all have transitions of the same or equivalent energies to within an average of about 1 keV–almost identical. Furthermore, it is found that transitions of the same energy do not always connect levels of the same spin, indicating noncollective angular momentum alignments that are all very nearly integers (0, 1ħ, or 2ħ). Possible explanations involving pseudospin are discussed.

We have observed Doppler-shifted x rays characteristic of Sb and Sn atoms in coincidence with ${}_{}{}^{108}{}_{}{}^{}\mathrm{Xn}$ evaporation residues resulting from the emission of four protons by the compound nucleus (CN) formed in the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${+}^{54}$Fe. We have attributed the Sb x rays to atomic inner-shell vacancies which are created on the way into the nuclear reaction and filled before the emission of the last proton in the deexcitation cascade. The mean proton partial width of the nuclear states, formed at a mean excitation energy of 25±4 MeV by the evaporation of three protons by the CN, has been deduced.

Fission-fragment angular distributions in reactions of ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{232}$Th and ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$, and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{237}$Np have been measured. While the measured anisotropies in B- and C-induced fission are found to be in agreement with the predictions of the standard Halpern-Strutinsky theory, they are anomalously large in the case of O- and F-induced fission. Such a discontinuous behavior in angular anisotropy with respect to the entrance-channel mass-to-charge asymmetry provides an experimental verification of the predictions of the preequilibrium fission model proposed earlier to explain the anomalous fragment angular distributions.

The onset of chaos is investigated for excited, rapidly rotating nuclei, utilizing a schematic two-body residual interaction added to the cranked Nilsson Hamiltonian. Dynamical effects at various degrees of mixing between regularity and chaos are studied in terms of fragmentation of the collective rotational strength. It is found that the onset of chaos is connected to a saturation of the average standard deviation of the rotational strength function. Still, the rotational-damping width may exhibit motional narrowing in the chaotic regime.

Partial decay schemes in the neutron-rich nuclei ${}_{}{}^{103}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{104}{}_{}{}^{}\mathrm{Zr}$ have been measured for the first time and rotational bands in ${}_{}{}^{100–102}{}_{}{}^{}\mathrm{Zr}$ have been extended to spins of up to 10ħ by observing prompt γ rays from the spontaneous fisson of ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$. These nuclei are among the most deformed known at low spin and excitation energy. The level structures in the odd-A nuclei show that the ${\mathit{h}}_{11/2}$ intruder orbital plays an important role in stabilizing the deformation in this region.

Lifetimes were measured for transitions in the superdeformed band of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Hg}$ with the Doppler-shift attenuation method. The results yield an essentially constant quadrupole moment of 20±2 e b and indicate that the sidefeeding lifetimes are of the same order as the state lifetimes. The data are consistent with calculations using the cranked Woods-Saxon Strutinsky method with pairing.