We demonstrate that cyclotron resonance with observed electric field fluctuations is responsible for production of the oxygen-ion conics that are observed by the Dynamics Explorer 1 satellite in the central plasma-sheet region of the Earth’s magnetosphere. The ion-velocity distribution is described by a quasilinear diffusion equation which is solved by the Monte Carlo technique. The acceleration produced by the observed wave spectrum agrees well with the ion observations, in both form and magnitude. To our knowledge, this represents the first successful comparison of an observed conic with any theoretical model.

In an experiment at Fermilab we have measured the lifetime of $K_S^0$ mesons produced by 800-GeV/c protons on tungsten. $K_S^0$→${\pi }^{+}$${\pi }^{\mathrm{-}}$ decays from 100 to 350 GeV/c, between 9.3 and 25.3 m from production, were selected for the measurement. The result was (0.8920±0.0044)×${10}^{\mathrm{-}10}$ sec, in excellent agreement with measurements performed for 2–5-GeV/c $K_S^0$. The lifetime was also calculated for seven momentum bins. The results were completely consistent with Lorentz invariance. No evidence was found for the mometnum dependence suggested by the intermediate-range ‘‘fifth-force’’ hypothesis.

We report on new measurements of the Λ and proton branching fractions and momentum spectra from B-meson decay. The large Λ-to-p ratio, the absence of B→ΛΛ¯X, and the presence of Λ-lepton charge correlations suggest that charmed baryons are produced in B decay. Under the assumption that all of the observed baryons are associated with charmed-baryon production, we find a B–to–charmed-baryon branching fraction of (7.4±2.9)%.

Single electrons and positrons have been alternately isolated in the same compensated Penning trap in order to form the geonium pseudoatom under nearly identical conditions. For each, the g-factor anomaly is obtained by measurement of both the spin-cyclotron difference frequency and the cyclotron frequency. A search for systematic effects uncovered a small (but common) residual shift due to the cyclotron excitation field. Extrapolation to zero power yields $e^{+}$ and $e^{\mathrm{-}}$ g factors with a smaller statistical error and a new particle-antiparticle comparison: g($e^{\mathrm{-}}$)/ g($e^{+}$)=1+(0.5±2.1)×${10}^{-12}$. . AE

A new decomposition of the multichannel scattering matrix, valid near an isolated, narrow resonance, is presented. It is consistent with the theory of single-channel resonances, and readily provides transition probabilities for inelastic resonant collisions. Some features of the formalism are illustrated by a vibration-rotation resonance in three-dimensional H + CO.

We consider the chiral bag model recently proposed in which an exterior Skyrme soliton interacts with the interior quarks through the imposition of the continuity of the axial-vector current at the surface. We propose the introduction of the ω meson to enforce, in addition, continuity of the baryon density. We obtain unique values of ${\mathrm{g}}_{\mathrm{\pi }\mathrm{NN}}$, the bag radius, the nucleon-Δ mass, and the isoscalar radius which reproduce the experimental data to within about 20%.

First evidence of the nucleus ${}_{}{}^{22}{}_{}{}^{}\mathrm{Si}$ (${\mathrm{T}}_{\mathrm{z}}$=-3) is observed by fragmentation of 85-MeV/nucleon ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ projectiles from the Grand Accélérateur National d’Ions Lourdes.

We have studied ${\mathrm{H}}^{+}$+He ionizing collisions, and find that electrons stranded between the two postcollision Coulomb centers dominate the ejected-electron spectra for intermediate (∼100 keV) projectile energies. The importance of these electrons is clearly established by our classical calculations which are in qualitative agreement, in both shape and magnitude, with experimental spectra taken by us, and with earlier measurements. These ‘‘saddle-point’’ electrons are produced by a classically understandable mechanism, and are unambiguously observed at nonzero scattering angles.

Collisional damping can induce a coupling between two nonresonant light beams propagating in an atomic vapor. This coupling is sufficiently important to induce a gain process for a weak probe beam interacting with an intense pump beam. We present here the first observation of a cw oscillation generated by this process using a cell which contains sodium and helium, the pump beam being slightly detuned from the ${\mathrm{D}}_2$ resonance line. We also show how the self-oscillation due to four-wave mixing is modified by the presence of a buffer gas.

The properties of a beam generated by self-oscillation due to four-wave mixing in a cavity are described. The experiment is performed in sodium vapor, in continuous-wave regime. This system exhibits an unusually low threshold condition. The output power is of the order of 1 mW and the oscillation is almost always bistable. Phase locking and huge phase-sensitive noise are observed on this oscillating beam.

For high-density Ohmic discharges in the TEXT (Texas Experimental) tokamak, a distinct ion mode (i.e., density fluctuations propagating in the ion diamagnetic drift direction) is observed in the microturbulence spectra. The magnitude and spectral characteristics of this mode are identified. Onset of the ion feature occurs at plasma densities where a clear saturation is evident in the global energy-confinement time ${\tau }_E$. A possible connection between this experimentally observed ion mode and the theoretically predicted properties of instabilities driven by ion temperature gradient (${\eta }_i$) is explored.

When an intense electromagnetic wave is incident obliquely on a sharply bounded overdense plasma, strong energy absorption can be accounted for by the electrons that are dragged into the vacuum and sent back into the plasma with velocities v≃$v_{\mathrm{osc}}$. This mechanism is more efficient than usual resonant absorption for $v_{\mathrm{osc}/\mathrm{\omega }>\mathrm{L}}$, with L being the density gradient length. In the very high-intensity ${\mathrm{CO}}_2$-laser–target interaction, this mechanism may account for most of the energy absorption.

The dynamics and energy flow in Au plasmas produced by a 0.35-μm laser have been studied with layered targets with 6- and 24-beam spherical illumination from the Omega laser, to understand the processes leading to sub-keV x-ray emission. A significant enhancement in x-ray conversion at low intensities is observed for the 24-beam irradiations with higher energy, greater uniformity, and larger targets. Results are interpreted by comparison with hydrodynamics code calculations. The depth of energy penetration and x-ray emission in the plasma appears to be well understood, but some details of the x-ray time signatures and spectra are not.

This paper demonstrates that a wide range of driven, overdamped, nonlinear systems can exhibit negative differential resistance, where the equilibrium amplitude of oscillation decreases as the amplitude of the driving force increases. As an example we examine the response of a parametrically driven bistable electronic circuit to both a dichotomous and a sinusoidal driving force. A general condition is derived for the onset of negative damping in the presence of a large-amplitude modulation.

Free-electron lasers in the electron cyclotron frequency range have been proposed as an efficient means of heating and driving current in tokamak plasmas. The proposed free-electron laser will have short pulses (≊5×${10}^{\mathrm{-}8}$ sec) with a peak power of (4–8)×${10}^9$ W and electric fields within the plasma in the range ${10}^5$–${10}^6$ V/cm. At these high intensities nonlinear effects compete with thermal effects in the absorption of microwave power. Analytic and numerical calculations of the nonlinear absorption are presented.

The phases of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ adsorbed on graphite are simulated by use of the Feynman path-integral Monte Carlo method. The fluid, commensurate solid, incommensurate solid, and reentrant fluid phases are found and are in agreement with the experimental phase diagram. The microscopic structure of the reentrant fluid is observed to be a striped domain-wall liquid and is consistent with a recent experimental interpretation and theoretical model. Larger-size systems are required for further quantitative analysis of the domain-wall liquid.

It is argued that NMR measurements can be used to help resolve whether the cholesteric fog phase (blue phase III) has an icosahedral quasicrystalline structure. The theoretical spectrum is calculated and found to differ from those both predicted and observed for the cubic blue phases. Some promising materials for experimental studies are suggested. The method developed to calculate the theoretical spectrum is new and should be useful for the study of other properties of quasicrystals.

Lamellar eutectics only grow in steady state over a small range of melt compositions between the two solidus lines of a binary phase diagram. Outside this range their growth exhibits a rich dynamical behavior. A random-walk model is constructed to simulate eutectic solidification of a thin film and applied to study this behavior. In addition to oscillatory modes, a ‘‘tilting instability’’ on the lamellar spacing is found at off-eutectic compositions. Well into nonlinear regimes, this instability causes lamellae from the minor phase to follow convoluted solidification paths thereby generating exotic eutectic textures.

Carbon films on a Ni(111) surface are deposited from 1–300-eV mass-selected ${\mathrm{C}}^{+}$ beams in a UHV chamber and the energy and dose dependence of the C Auger line shape is monitored. Initial deposition forms a carbide structure which is chemically bonded to the surface. The Auger line shape evolves with increasing ${\mathrm{C}}^{+}$ dose into that of a diamondlike structure for ion energies in the range 10–300 eV. Features of the x-ray and the ultraviolet photoemission spectra support this interpretation. The diamondlike films do not chemisorb ${\mathrm{O}}_2$, have a low sputtering yield with ${\mathrm{O}}^{+}$ ions, and exhibit a higher thermal stability than the carbidic films; these results are discussed in terms of a qualitative model.

We propose and demonstrate here a criterion, based on thermal expansion, which discriminates unambiguously between ‘‘floating’’ and ‘‘locked’’ layers. The first observation of a phase transition between an incommensurate ‘‘floating’’ and a high-order commensurate ‘‘locked’’ phase in two dimensions is reported. High-resolution He-diffraction results show a first-order transition in Kr layers on Pt(111) at coverages of ∼0.8 monolayer with a lattice-parameter jump of ∼0.1 Å. In the ‘‘locked’’ phase every sixth Kr atom is located at a preferred adsorption site (threefold hollow) forming a hexagonal (5×5)R0° superstructure.