Absorption and energy partitioning have been measured for spherical targets irradiated on the OMEGA facility by six beams of nanosecond 351-nm laser radiation at intensities from ${10}^{13}$ to ${10}^{15}$ W ${\mathrm{cm}}^{-2\mathrm{}}$. Efficient collisional absorption is found, in agreement with one-dimensional simulations including refraction and inhibited transport, and very low levels (∼${10}^{-4\mathrm{}}$) of superthermal electron production are demonstrated.

The diagnosis of a dense, cold, laser-induced, metal-vapor plasma by laser scattering techniques is reported here for the first time. The scattered spectra obtained at 90° with scattering parameter $\alpha =1.5-3\mathrm{}$ showed evidence of temperature inhomogeneities and/or plasma-wave damping by electron-ion collisions. The total scattered-light intensity could be explained by inclusion of a Ray-leigh scattering contribution from the cesium $6s-6p$ blue wing. These results also represent the most non-Debye plasmas investigated to date by scattering.

The cubic direct-interaction approximation is applied to the truncated cubically nonlinear Schrödinger equation. The statistical theory does a satisfactory job in several important respects.

We report here on the first measurements of decay times, during the beam pulse, of plasmas generated by intense relativistic electron beams. The pressure scaling of characteristic decay times and detailed temporal evolution are consistent with a simple plasma-electron generation model which includes direct-impact ionization, avalanche, and recombination. The decay times have been correlated with observed frequencies of the beam resistive hose instability, and the inverse relationship between $\omega$ and $\tau$ predicted by linear theory has been experimentally verified.

The antenna structure in the TCA tokamak is phased to excite preferentially Alfvén waves with known toroidal and poloidal wave numbers. Surprisingly, the loading spectrum includes both discrete and continuum modes with poloidal wave numbers incompatible with the antenna phasing. These additional modes, which are important for our heating experiments, can be attributed to linear mode coupling induced by the toroidicity of the plasma column, when we take into account ion-cyclotron effects.

Cooperative effects during both alkali-Ca and Na-K migration under electron irradiation of glasses have been pointed out for the first time by analysis of experimental data in the framework of the thermodynamics of irreversible processes.

We present a new formulation for simulations of metallic systems which allows for volume and shape variations and incorporates explicitly the dependence on density of the "volume energy" and the effective pair potentials. Simulations of liquid Mg yield good agreement with experiments for several properties including internal energy, density, and structure factors at several temperatures ($T$) and pressures ($P$). Correlations between fluctuations in $T$, $P$, and volume are in approximate agreement with the appropriate thermodynamic relations.

The diffusivity of hydrogen in tantalum was measured by means of the perturbed-angular-correlation technique. The method makes use of the radioactive decay of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Hf}$ to ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ and the possibility of the trapping of hydrogen at an impurity and the release of it after the nuclear conversion.

Lamellar systems which are close to microemulsions in the phase diagram are observed for the first time by quasielastic light scattering. The observed hydrodynamical mode is attributed to the collective undulations of the lamellae and allows us to determine the rigidity constant of the interfacial film. The results emphasize the role of the cosurfactant (alcohol) in the transition from organized phases (lamellar and birefringent) towards isotropic phases (droplet microemulsions).

We consider the influence of thermal fluctuations on systems with negligible surface tension ("membranes"), whose behavior is determined by curvature effects. Fluctuations change the effective rigidity and other relevant parameters. Two-dimensional membranes appear rigid at short distances and crumpled at long distances. For more than two-dimensional membranes (or in presence of long-range forces) a crumpling transition separates a rigid low-temperature phase from a crumpled high-temperature one.

X-ray scattering measurements are reported for critical smectic-$A_2$ fluctuations along a line of second-order transitions between the smectic-$A_1$ and smectic-$A_2$ phases in mixtures of hexylphenyl cyanobenzoyloxy benzoate (D${\mathrm{B}}_6$) and terephthal-bis-butylaniline (TBBA). The measured exponents $\gamma =1.46\mathrm{}\pm 0.05$ and ${\nu }_{\parallel }={\nu }_{\perp }=0.74\mathrm{}\pm 0.03$ are constant along the second-order line and agree with recent heat-capacity measurements and the scaling law, $3\nu +\alpha =2\mathrm{}$. They disagree with current theoretical expectations.

We report the first two-dimensional momentum measurements of annihilating positron-electron pairs at a solid surface. Positrons of 18 keV or 740 eV impinged on a clean Cu(121) surface. The 740-eV spectrum was resolved into two components, one associated with energetic positronium emission displaced from zero momentum and a second centered on zero momentum with distinct asymmetry for the directions parallel and perpendicular to the surface. The 18-keV spectrum was dominated by positron Bloch-state annihilation.

Using a high-intensity beam of 200-eV positrons we have measured the two-dimensional angular correlation of the $2\gamma$ annihilation radiation from a clean Al(100) surface. The momentum distribution identified with the positron surface state has a nearly isotropic conical shape and a (7.1 ± 0.5)-mrad full width at half maximum. The data are not consistent with a simple interpretation based on either the usual model of a positron bound in a surface state by its "image-correlation potential" or a positronium atom weakly bound to the surface.

Two-dimensional magnetoplasmons are studied in a classical gas of electrons bound to a liquid-helium surface. A new and unpredicted resonant mode has been observed. The density and magnetic field dependences of this new mode differ strikingly from normal magnetoplasmons. These new resonant modes are interpreted as edge magnetoplasmons of the two-dimensional charge sheet.

We have shown that the collective modes of a bounded two-dimensional plasma in a magnetic field exhibit unexpected features which are dynamical manifestations of the Hall effect. In high fields we observed the appearance of a novel magnetically localized one-dimensional wave which propagates along the perimeter of the plasma.

Frequency-dependent proton and fluorine NMR experiments have been performed on tetrathiafulvalene-Au${\mathrm{S}}_4$${\mathrm{C}}_4$${\left(\mathrm{C}{\mathrm{F}}_3\right)}_4$, which give the first experimental evidence for the incommensurate nature of the high-field phase in spin-Peierls systems. The field-induced transition to this phase is found to be first order at low temperatures. The echo shape in the high-field phase is described in terms of a soliton-lattice model due to Nakano and Fukuyama.

New results for the magnitude of flicker noise, considered as resistance fluctuations, in random resistor networks are reported. Near the percolation threshold $p_c$, the magnitude of the relative noise is shown to diverge as ${(p-p_c)}^{-\kappa }$. The new exponent $\kappa$ is calculated by various methods: Monte Carlo simulations, effective-medium theory, and position-space renormalization group. Exponents pertaining to higher-order cumulants of the resistance fluctuations are also calculated. The possible implications of our results for ongoing experiments on metal-insulator mixtures and cermets are also discussed.

Pulsed-field-gradient NMR was used to examine translational diffusion of the oil, water, and surfactant components in a microemulsion. The diffusion of both oil and water shows a smooth variation along a line in the phase diagram where two-phase/three-phase/two-phase transitions are encountered, and the diffusion is unrestricted and three dimensional. Dynamic structural effects are needed to interpret the results. Surfactant diffusion reaches a peak in the three-phase region.

The response of a damped anharmonic oscillator, being a model for many systems that undergo a bifurcation, is determined in the presence of small-amplitude parametric modulation of arbitrary dynamics and statistics. Inertia always stabilizes the trivial state and suppresses the growth of the bifurcating solution above the shifted stability threshold. The size of both effects depends on the modulation spectrum. Explicit formulas for threshold, bifurcating solution, and moments are given.