It is shown that a plasma produced by a Marshall gun can be injected into and trapped by a tokamak plasma. Gun injection raises the line-averaged density and peaks the density profile. Trapping of the gun-injected plasma is explainable in terms of a depolarization current mechanism.

The stimulated-Raman-scattering instability in a C${\mathrm{O}}_2$-laser-produced plasma is studied by picosecond-resolution Thomson scattering. The instability first appears near $\frac{0.25n}{n_c}$ and is observed to propagate to lower densities at the group velocity of electron plasma waves. Temporal growth rates are measured over the whole investigated density range ($0.15<~\frac{n}{n_c}<~0.25$) and are found to be 5 times smaller than absolute rates theoretically predicted for a finite plasma.

We have measured the velocity of propagation of the ${}_{}{}^3{}_{}{}^{}\mathrm{He} A-B$ interface as a function of temperature and pressure for the ${}_{}{}^3{}_{}{}^{}\mathrm{He}-A$ initially in a hypercooled state. Velocities as high as 67 cm/s have been observed. Nucleation of the $B$ phase occurred at greatly different temperatures in two different regions of the experimental cell.

We investigate the friction coefficient of the moving boundary. At not too low temperatures the friction is ascribed primarily to transmission and Andreev reflection of quasiparticles; the resulting theoretical value of the terminal velocity $v_{\mathrm{AB}}$ is in reasonable agreement with the data of Buchanan, Swift, and Wheatley. At lower temperatures we predict a saturation of $v_{\mathrm{AB}}$ and underdamped oscillations of the pinned boundary.

Nonequilibrium periodic textures are induced by a magnetic field $H$ applied to the aligned uniaxial (negative diamagnetic anisotropy) lyotropic nematic phase of the potassium laurate-decanol-water system. Two cases are studied: a rotating field and a static field. For the rotating field a transient one-dimensional structure results. With the static field, the appearance and decay of a two-dimensional lattice structure is observed. In both cases the dependence of the lattice periodicity on $H$ is measured and compared to recent theories.

In binary liquid mixtures, the growth of wetting layers can be limited by diffusion. At complete wetting, the distance $l$ between the interfaces bounding the layer is shown to grow as $l\left(t\right)\mathrm{}\approx A_{*}{t}^{\theta }$ for large times $t$ where $A_{*}$ increases near the consolute point. In three dimensions where this growth behavior should be accessible to experiments, $\theta =\frac{1}{8} \mathrm{and} \frac{1}{10}$ for nonretarded and retarded van der Waals forces, respectively. The interfacial motion resulting from diffusion-limited growth is studied for general interactions, and a planar interface is found to be stable for $\theta <\frac{1}{2}$.

Indirect interactions are shown to exist between two ions or atoms which are both first neighbors of a central ion. The interactions define a force tensor which has five nonzero components if the central ion has filled shells. These parameters are calculated for alkali halides and compare favorably to experiment. Pairwise-central-potential models appear to be inadequate to describe even simple insulators.

Size effects in fcc binary alloys undergoing a bulk first-order phase transition are investigated in the limit of very thin films. The interplay between surface segregation and spatial ordering is studied by means of a discrete model in the Bragg-Williams approximation. Concentration and long-range-order-parameter profiles in the film are calculated for equilibrium and for metastable states. Results for the thickness dependence of the transition temperature and of the discontinuity of the order parameter are presented.

Transmission-electron microscopy of chiral 4-(2-methylpentylphenyl)-4′-hexyloxybenzoate (CE4) quenched from its cholesteric and blue phases (BP) I and III are presented. Images of cholesteric and BP I are consistent with an earlier study of similar compounds. CE4 quenched from its BP III is a spaghettilike tangle of filamentary objects of 10- to 50-nm diameter and lengths of 0.1 to 1 μm. These are likely double-twist cylinders in a liquidlike arrangement, melted from their lattice structure in the BP I and II. BP III apparently has a basic, double-twisted structure whose sense and length scale correspond to BP I and BP II, but without the latter's long-range periodicity.

We have measured the superconducting transition temperature $T_c\mathrm{}\left(H\right)\mathrm{}$ as a function of magnetic field for a network of thin aluminum wires arranged in two quasicrystalline arrays, a Fibonacci sequence and the eightfold-symmetric version of a Penrose tiling. The quasicrystals have two periods whose ratio $\sigma$ is irrational and are constructed of two tiles with irrationally related areas. We find a series of dips in $\delta T_c\mathrm{}\left(H\right)\mathrm{}$ corresponding to favorable arrangements of the flux lattice on the quasi-crystalline substrate. The largest dips are found at ${\sigma }^n$ and the dips approach the zero-field transition temperature as $n$ increases.

A new incommensurate magnetic phase has been found in europium triarsenide which belongs to a novel class of layered semimetallic compounds. This incommensurate phase develops below $T_{\mathrm{N}}=11.30\mathrm{}$ K and is followed by a lock-in transition to a commensurate phase at $T_L=10.26\mathrm{}$ K. Although this happens at a zone-boundary wave vector, the transition is nearly continuous. We propose an interpretation of the very smooth temperature dependence of the modulation vector in terms of the soliton lattice model.

Using a beam of slow positrons in ultrahigh vacuum, we estimate the positron mean free path and energy-loss rate and measure the inelastic thresholds due to exciton, electron-hole pair, and positronium formation in solid rare-gas targets. The measurements are used to explain the large emission energies of positrons from the wide-band-gap solids in terms of a hot-positron model. The large diffusion length of the hot positrons in the solid rare gases makes them very efficient moderators for producing slow positrons.

We study the plasma excitations of an array of two-dimensional electron-gas layers arranged in a Fibonacci sequence. The plasmon spectrum is analyzed by a transfer-matrix method. It is shown that the spectrum is always "critical," i.e., it corresponds to neither extended nor localized plasmon states. This property is reflected in the calculated Raman intensities.

Translational and rotational energy distributions of NO molecules scattered from an oxidized Ge surface were determined by means of laser two-photon ionization and time-of-flight techniques. Trapping-desorption and direct inelastic-scattering channels are clearly separated in state-resolved measurements: The former shows a mean kinetic energy $〈E_{f,J^{\prime \prime }}〉$ corresponding to the surface temperature, while the latter exhibits "rainbow" features and a $〈E_{f,J^{\prime \prime }}〉$ which is, for high-$J^{\prime \prime }$ states, much larger than expected from pure translational to rotational energy conversion.

The local susceptibility and $3d$-spin dynamics of isolated Fe ions recoil implanted into alkali-metal hosts is measured by the perturbed-$\gamma$-ray-distribution method. The observations of extremely large values for the hyperfine fields and magnetic moments and of an extremely small spin linewidth are quantitatively consistent with a stable $3d^6$ configuration of ${\mathrm{Fe}}^{2+}$ ions in spin-orbit coupling along with a negligible crystal-field splitting. Fe in Li strongly deviates from the magnetic behavior of a purely ionic configuration. The results permit a comparison of local-moment formation of $3d$ with $4f$ systems.

The characterization problem of the inverse data $T$ associated with the inverse scattering for $N$ hyperbolic equations in $n+1\mathrm{}$ dimensions, $n>\mathrm{}1\mathrm{}$, is explicitly solved. A simple relationship is found between $T$ and the scattering amplitude $S$; if $N=3\mathrm{}$, $T=S$. The potential can be reconstructed by just the solving of two hyperbolic equations in two dimensions. The $N$ wave interaction equations are reduced from $n+1\mathrm{}$ to two spatial dimensions.

We investigate the kinetics of a coagulation process involving two distinct bifunctional monomeric species $A$ and $B$ (which can be ascribed a positive and negative "charge," respectively) with bonding allowed only between $A$ and $B$. When the rates for charged-charged, neutral-neutral, and neutral-charged reactions are all distinct, we find, from the solution to the mean-field rate equations, that (i) the kinetic exponents are nonuniversal and (ii) a scaling description of the clustersize distribution fails. Similarly intriguing results are also found for the kinetic behavior below the upper critical dimension.

We show that the hypothesis of an underlying quaternionic dynamics for particle physics naturally implies an effective complex $\mathrm{CP}$-nonconserving interaction of superweak form, but arising in second order in the quaternionic perturbation. The energy scale for the appearance of strong quaternionic effects is estimated to be 20 TeV.

A chiral-invariant effective Lagrangean is constructed from pions and the low-mass measons. Soliton solutions of this Lagrangean are investigated. These are used to predict properties of baryons. The agreement with experiment is quite satisfactory in spite of very limited freedom in the choice of the parameter values. This gives strong support to the idea that qualitatively and even semiquantitatively baryon physics can be deduced from meson physics via solitons.

We have performed absolute measurements of the differential cross section for elastic $e-p$ scattering in the range of momentum transfer from $Q^2=2.9\mathrm{} \mathrm{to} 31.3$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. Combined statistical and systematic uncertainties in the cross-section measurements ranged from 3% at low $Q^2$ to 19% at high $Q^2$. These data have been used to extract the proton magnetic form factor $G_M^p\left(Q^2\right)$. The results show a smooth decrease of $Q^4{G}_M^p$ with momentum transfer above $Q^2=10\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. These results are compared with recent predictions of perturbative QCD.