Quasielastic-light-scattering measurements were made on microemulsions in which the apparent volume fraction $\phi$ of the microemulsion droplets was varied from 0.1 to 0.75. The density correlation function shows an exponential decay at short time but deviates from it at long time especially for intermediate $\phi$. The initial decay rates of the correlation functions decrease steadily as a function of $\phi$, reaching a minimum at ${\phi }_c=0.62\mathrm{}$, and increase thereafter. The overall time dependence of the correlation functions can be fitted by the function $\exp [-{\left(\frac{t}{T}\right)}^{\alpha }]$; the exponent $\alpha$ varies from 1 down to 0.66 and back up again to 0.9 over the range of $\phi$.

A simple computer model of viscous fingering in a porous medium is presented, together with experimental results for fingering of oil into glycerine in etched-glass networks. The model treats the medium as a square lattice of connected tubes with randomly chosen radii. By Monte Carlo simulation it is demonstrated that for a narrow size distribution of tubes the fingers form ordered patterns (dendrites) with growth mostly along the coordinate axes, but for a wide size distribution the fingers form a chaotic structure with a fractal dimension around 1.72. Qualitatively similar behavior is seen in the experiments.

A Monte Carlo study of spherical particles shows that increased interaction strength may either raise or lower the volume fraction required for percolation. The sense of the change depends on the distance at which two particles are considered connected, the dimensionality, and the proximity to the critical temperature. An on-lattice simulation supports the continuum result.

Ginzburg-Landau-Gor'kov equations and the expression for the current for coexisting superconductivity-charge-density-wave (CDW) systems near the superconducting transition temperature have been derived from microscopic theory. Two particular features are discussed: an additional current due to the sliding CDW, and the CDW-induced anisotropy, which lead to interesting physical consequences including the Meissner effect with a contribution from both currents. Measurements of CDW-induced anisotropy can be used to probe the microscopic mechanism of coexistence.

Vibrationally excited NO molecules have been observed in the scattering of $\mathrm{NO}\mathrm{}(v=0\mathrm{})\mathrm{}$ from Ag(111). A direct mechanism is inferred based on the observation of $v=1\mathrm{}$ angular distributions, which are quasispecular, and rotational-state distributions, which depend on beam energy. Vibrational excitation is found to depend strongly on surface temperature, $T_S$, and relatively weakly on incident kinetic energy, $E$, reaching (∼7±5)% at $T_S=760\mathrm{}$ K and $E=120\mathrm{}$ kJ ${\mathrm{mol}}^{-1\mathrm{}}$. These results are discussed in terms of an electronic mechanism for vibrational excitation.

The escape rate of an underdamped ($Q\approx 30$), current-biased Josephson junction from the zero-voltage state has been measured. The relevant parameters of the junction were determined in situ in the thermal regime from the dependence of the escape rate on bias current and from resonant activation in the presence of microwaves. At low temperatures, the escape rate became independent of temperature with a value that, with no adjustable parameters, was in excellent agreement with the zero-temperature prediction for macroscopic quantum tunneling.

Normal-emission angle-resolved photoemission data from Na(110) are presented. Two discrepancies between these data and the predictions of free-electron theory are observed. First, the occupied-band width is 2.5 eV, while theory predicts 3.2 eV. Second, the bands near the Fermi level appear to have been severely distorted, as could be produced by a charge-density wave oriented normal to the surface.

Angle-resolved photoemission perpendicular to the surface of a Na or K film (for photon energies near 35 and 26 eV, respectively) can reveal the momentum mixing and band bending caused by the charge-density-wave potential.

Survival of vibrational excitation has been observed for the scattering of NO prepared by a laser in a single well-defined quantum state, No ($v=1\mathrm{}$, $J=\frac{3}{2}$, $\Omega =\frac{1}{2}$), from a cleaved LiF(100) surface. State-selective angular, velocity, rotational, and electronic distributions of these vibrationally elastically scattered molecules have also been obtained for the first time.

Novel radio-frequency NMR pulse sequences are presented and their application to imaging of solids with use of rf field gradients is discussed. The sequences cause a nuclear spin to precess about the static field direction at a rate proportional to the strength of certain of the pulses. This forced precession is independent of the resonance offset and of couplings to other spins. The pulse-sequence design is described by means of coherent averaging theory and is confirmed experimentally and numerically.

The mean-field Fröhlich Hamiltonian in one dimension is diagonalized numerically in a self-consistent manner for systems with a nearly ½-, $\frac{1}{3}$-, or ¼-filled band. Near the Fermi energy, midgap states are present inside the main gap, and the location of the midgap states is not right in the center of the main gap. Recent absorption experiments on orthorhombic Ta${\mathrm{S}}_3$ are analyzed in terms of the above results.

We present measurements and analysis of the basal thermal conductivity for two dichalcogenides: $1T$-Ta${\mathrm{S}}_2$ and $2H$-Ta${\mathrm{Se}}_2$. The data which are obtained for the first time cover the range 80-400 K. The lattice contribution is important for each compound and possesses specific features related to charge-density-wave-type transitions; in particular, that of Ta${\mathrm{S}}_2$ exhibits a quite unusual upward jump. For Ta${\mathrm{Se}}_2$ we use an order-disorder picture to explain both the lattice conductivity and the entropy variation in unison with the electrical resistivity.

$\beta$-delayed neutron-emission probabilities of neutron-rich S to K isotopes are calculated with nuclear-structure effects taken into account. These results strongly affect predictions made in high-neutron-density astrophysical scenarios for isotopic abundances of several elements. In particular, it is demonstrated that the solar abundance ratio ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$/${}_{}{}^{46}{}_{}{}^{}\mathrm{Ca}$ as well as the correlated Ca and Ti isotopic anomalies can be explained by the same nucleosynthesis process.

We extend the region of applicability of phase-space techniques, for the study of quantum systems, by developing an expansion for the Wigner distribution function and correlation functions, in powers of an interaction potential. These results are not restricted to the near-classical regime (expansion in powers of ħ), in contrast to the Wigner-Kirkwood expansion. The relation to other perturbation methods (Lindstedt-Poincaré, Green’s function) is explored.

The steady-state particle density n¯ and the relaxation time τ of homogeneous density fluctuations are calculated for one-dimensional systems in which particles move diffusively and annihilate irreversibly, and steady sources of either single particles (model I) or pairs of neighboring particles (model II) are also present. For small particle-production rates h, we find n¯∼${\mathrm{h}}^{1/\mathrm{\delta }}$ and τ∼${\mathrm{h}}^{\mathrm{-}\mathrm{\Delta }}$ with δ=3, Δ=(2/3) for model I and δ=2, Δ=1 for model II. If we interpret particles as solitons, model II is used to account for some aspects of the experimental data on the photoinduced absorption of trans-(CH${)}_{\mathrm{x}}$.

Successive-subharmonic-oscillation cascade up to the fifth order followed by chaotic emission (parametric instability) is experimentally observed for the first time in an AlGaAs laser diode coupled to an external cavity. This phenomenon is attributed to the nonlinear interaction between the lasing and amplified-spontaneous-emission modes through the refractive-index dependence on carrier density in the active layer. Observed instabilities are successfully reproduced by the numerical simulations based on the generalized van der Pol equations including the asymmetric intermode interaction.

Chiral-symmetry breaking in (2+1)-dimensional QED is studied in the many-flavor limit. Analytical and numerical solutions of the Dyson-Schwinger equation are found. Substitution of the symmetry-breaking solution in the composite-operator effective potential indicates that it is favored over the symmetric solution. Improvements and possible extensions of the analysis are discussed.

We show that the Hamilton-Jacobi equation for Nambu-Goto strings in three dimensions is given by 1/2${\mathrm{F}}_{\mathrm{\mu }\nu }$${\mathrm{F}}^{\mathrm{\mu }\nu }$=-(2πα’${)}^{\mathrm{-}2}$, where ${\mathrm{F}}_{\mathrm{\mu }\nu }$(x)=${\mathrm{\partial }}_{\mathrm{\mu }}$${\mathrm{A}}_{\nu }$-${\mathrm{\partial }}_{\nu }$${\mathrm{A}}_{\mathrm{\mu }}$. We also find string wave equations satisfied by functionals of lines (paths), which reduce to the Hamilton-Jacobi equation in the classical limit. In more dimensions these string wave equations describe a restricted class of Nambu-Goto strings.

We present evidence for the radiative decay J/ψ→γωω with a branching fraction of (1.76±0.09±0.45)×${10}^{\mathrm{-}3}$. The ωω invariant-mass distribution peaks at 1.8 GeV/$c^2$, just above threshold. Analysis of angular correlations indicates that ωω system below 2 GeV/$c^2$ is predominantly pseudoscalar. Upper limits are presented for the branching fractions of ωω decays of the θ(1690), the $g_T$ states near 2.2 GeV/$c^2$, and the ${\eta }_c$.

The γ radiation from ${}_{}{}^{153}{}_{}{}^{}\mathrm{Ho}$ has been measured with Compton-suppressed Ge detectors. At least four components can be identified; the energy and spin removed by each of these have been measured, and their Doppler shifts analyzed. New fine structure is observed in the pre-yrast γ spectrum which arises from single-particle transitions forming the link between the yrast and continuum cascades. Near the yrast line the single-particle character of the states is preserved, but at higher energies collective modes begin to dominate.