The analyzing power (spin-dependent azimuthal asymmetry) has been observed for the first time in the nuclear Coulomb coherent production process, the ‘‘Primakoff process,’’ with the use of the newly constructed 185-GeV/c Fermilab polarized proton beam. We have observed a large asymmetry of this process in the regions of ‖t’‖<0.001 (GeV/c${)}^2$ and 1.36${\pi }^0$p)<1.52 GeV/$c^2$, where the Coulomb process is predominant. The measured asymmetry is consistent with the analyzing power of the existing low-energy γ+p→${\pi }^0$+p data.

Recent claims that the European Muon Collaboration (EMC) data on polarized proton structure functions violate quantum chromodynamics are shown to be unfounded and driven by the use of an incorrect or outdated balue of the F/D ratio for hyperon decays. Conclusions from the EMC experiment as to the amount of strange-sea polarization are rather sensitive to this value. Contrary to some statements in the literature, elastic-neutrino-scattering data are consistent with vanishing strange polarization.

A variational method is used to study the ground state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Expectation values are computed with a cluster expansion for the noncentral correlations in the wave function; the central correlations and exchanges are treated to all orders by Monte Carlo integration. The expansion has good convergence. Results are reported for the Argonne $v_{14}$ two-nucleon and Urbana VII three-nucleon potentials.

The depolarization parameter D in proton${\mathrm{-}}^{13}$C elastic scattering at 72 MeV has been measured with an accuracy of 0.003–0.004 per data point. D was found to deviate from unity by ∼0.02 around 65°, which is unambiguous evidence for a nucleon-nucleus spin-spin interaction. The data are well described by a microscopic calculation as well as by a phenomenological optical-model potential, which includes a real spherical spin-spin potential of strength $V_{\mathrm{ss}=0.7\mathrm{}\pm 0.1}$ MeV.

We have studied particle emission following ${\pi }^{+}$ absorption on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ at $T_{\pi }$=150 MeV by using a large-solid-angle detector. We find an absorption cross section leading to two or more energetic protons in the final state to be 98±15 mb. We find that only about 65 mb can be explained as quasideuteron absorption.

In a model study, yrast band-crossing structures are shown to be qualitatively changed by residual neutron-proton interactions. This could explain some anomalies recently observed for light Kr isotopes. Large effects on the yrast-band g factors are predicted.

Charge-changing processes have been investigated for 267–320-MeV ${\mathrm{Ti}}^{19+}$ and ${\mathrm{Ti}}^{20+}$ ions channeled in a thin gold crystal. High-resolution measurements of the energy losses suffered by the charge-changed ions show that electron capture by the well-channeled particles is significantly enhanced when the projectile velocity corresponds to ejected KLL Auger-electron energies from doubly excited states in the rest frame of the ion. The measurements of dielectronic capture exhibit exceedingly narrow resonance widths and reveal a shift of the resonances toward higher energies.

A pair of generalized coordinates is introduced to describe Wannier threshold effects in three- and four-particle systems. In the case of four-particle breakup, they indicate the presence of multiple unstable normal modes in the breakup configuration and thus reveal a new feature in the Wannier formalism: the occurrence of a secondary Wannier power law. This prediction is in accord with recent experimental observations of a break in the cross section near threshold for triple photoionization in oxygen and in neon.

Two different angular wave functions of the Ca(4${\mathit{p}}^2$${\mathrm{}}^1$${\mathit{D}}_2$) state are prepared via a two-step laser excitation with parallel and perpendicular configuratons of the two linear polarizations. These wave functions exhibit dramatically different alignment effects for the electronic energy-transfer process: Ca(4${\mathit{p}}^2$${\mathrm{}}^1$${\mathit{D}}_2$)+Ne → Ca(3d4$p^1$$F_3$) +Ne. Relative cross sections for individual Ca${\mathrm{}}^1$${\mathrm{D}}_2$ magnetic sublevels are obtained from these measurements using the rotation properties of the two wave functions.

Rank-4 alignment in near-resonant charge-transfer collisions has been observed for the first time. The general formula for describing the scattering intensity for cylindrical symmetry, in terms of multipole moments, from atoms excited by two parallel polarized lasers has been derived and used to evaluate the experimental results. A strong energy dependence of the relative charge-transfer cross section of the 4dσ, 4dπ, and 4dδ sublevels for the ${\mathrm{K}}^{+}$Na(4D)→${\mathrm{K}}^{\mathrm{*}}$+${\mathrm{Na}}^{+}$ system has been found.

An experiment studying the influence of molecular rotation in HI on photoelectron-spin polarization is presented. The experiment is highly wavelength selective since a laser-based vacuum-ultraviolet-radiation source with a bandwidth of 0.5×${10}^{\mathrm{-}4}$ nm is applied to produce circularly polarized light. Although in the Fano effect the kinetic energy of the photoelectrons is not analyzed, rotational structure is resolved via narrow-band excitation of autoionization resonances. The photoelectron-spin polarization is found to be strongly affected by the rotational substructure, leading to changes in both magnitude and sign for different rotational lines.

Amplitude fluctuations of the light from a semiconductor lase, operating 4 K, have been measured to be 11% below the shot-noise limit in the detected photocurrent. Weak optical reflection into the laser reduces the squeezing from the expected detector-current–to–laser-current transfer ratio of 25%. Results compare favorably with a theory which includes effects of optical feedback.

Multiphoton ionization of atomic hydrogen is investigated experimentally in the short-pulse regime (τ≤0.5 ps) at wavelengths around 600 nm and intensities up to ${10}^{14}$ W/${\mathrm{cm}}^2$. Sharp peaks in the energy spectrum of the photoelectrons can be attributed to resonant ionization processes via excited states which are ac-Stark shifted into resonance. Energies and angular distributions of the electrons allow one to identify some participating excited states with quantum numbers n≥4 and l≥3.

We describe experiments that show collective behavior in clouds of optically trapped neutral atoms. This collective behavior is demonstrated in a variety of observed spatial distributions with abrupt bistable transitions between them. These distributions include stable rings of atoms around a small core and clumps of atoms rotating about the core. The size of the cloud grows rapidly as more atoms are loaded into it, implying a strong long-range repulsive force between the atoms. We show that a force arising from radiation trapping can explain much of this behavior.

The correlations between a homoclinic orbit (HMO) and coherent patterns in the nonlinear Schrödinger model are discussed. In a Hamiltonian situation, two independent patterns are revealed to exist: One corresponds to a motion within an HMO, and the other outside of an HMO. The study further illustrates, when the Hamiltonian constraint is released, the significance of an HMO on the patterns dynamics by presenting the irregular HMO crossings and the resulting chaotic selections between the patterns.

The intermittent fine structure of fully developed turbulence is studied by means of a visualization experiment. Characteristic locally ordered flow patterns, tentatively identified as layered vortex sheets, are observed.

We observed a shear-induced alignment of colloidal particles in a Brownian dynamics simulation carried out in the presence of an oscillating shear flow. As the shear rate γ is increased for temperatures near the melting point, we first observe shear thinning followed by a transition to a state with two-dimensional order in the plane perpendicular to the flow. In contrast to earlier nonequilibrium molecular-dynamics studies which also found a similar result, no thermostat is needed to keep the system stable.

An experimental study of stimulated Compton scattering (SCS) from resonant electrons in a laser-produced plasma is reported. Up to 1.9 kJ of 350-nm laser light was used to irradiate 3-μm-thick CH targets in 1.3 to 3.3-ns pulses at intensities up to 1.3×${10}^{15}$ W/${\mathrm{cm}}^2$. SCS was detected by making time-resolved measurements of the emission near 420 nm. The measurements are compared to the results of theoretical modeling.

We calculate the effective mass of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ impurity atoms in a film of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atoms adsorbed to a substrate. The calculated effective mas of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ impurity shows a strong dependence on the structure of the underlying ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ film. When both the coupling of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ impurity to the background and to other ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ impurities are taken into account, our values agree well with recent experiments by Wang and Gasparini [Phys. Rev. B 38, 11 245 (1988)]. It is suggested that the Fermi-liquid contribution to the effective mass is experimentally obsrevable.

We have conducted ultrasound pulse transmission experiments to investigate the pair-breaking edge for superfluid ${}_{}{}^3{}_{}{}^{}\mathit{B}$ in a magnetic field. The experiments were performed at ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ temperatures below 0.4${\mathrm{T}}_{\mathrm{c}}$, pressures between 6 and 29.3 bars, and ultrasound frequencies of 168.33, 137.6, and 107 MHz. We used both depressurization and demagnetization techniques to measure the linear and quadratic magnetic field dependence of the pair-breaking edge frequency. We obtain values for the Fermi-liquid interaction parameter ${\mathrm{F}}_2^{\mathrm{a}}$ from the coefficient of the linear term. The quadratic term is due to the energy-gap distortion and its value is consistent with calculations of Schopohl and Tewordt.