The calculations and the results that predicted a fast-sound mode in low- as well as high-density binary fluid mixtures are presented in detail. Kinetic theory was used, which allowed a detailed discussion of the microscopic dynamics of the fluid in terms of eigenmodes. The Bhatnagar-Gross-Krook approximation method extended to binary mixtures was employed to solve the appropriate kinetic equation and to obtain approximate eigenmodes of the mixture. The fast-sound mode appears far beyond the hydrodynamic regime as either an extension to higher wave numbers of the hydrodynamic sound eigenmode or as a kinetic eigenmode. Some recent and possible future experiments are discussed.

We point out a relation between the electron degradation spectra determined by two differing cross-section sets but subject to the same source. The relation takes a form of the Fredholm integral equation of the second kind and may be viewed as an alternative form of the Spencer-Fano equation. The relation leads to a precise definition of the partial degradation spectra of electrons of successive generations. It also provides a basis for the perturbation theory by which one calculates effects of small changes of cross-section data upon the electron degradation spectrum.

Using a schematic interaction we derive and solve temperature-dependent Thomas-Fermi equations for a quantum liquid droplet (nucleus, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, or similar) in its vapor atmosphere. The results depend on the initial size of the droplet in the iterative numerical procedure, thereby simulating on the computer condensation and evaporation of the unstable droplets. The stationary but unstable droplet configuration is evidenced by a slowing down of the iterative change of the density. We also take into consideration bubble formation and instability for a chemical potential below the Maxwell liquid-vapor equilibrium value.

The ground state of a quantum strongly coupled one-component plasma, with planar symmetry, is analyzed. The analysis was done working with the deformable jellium model and the particle-particle interaction as a screened Coulombic potential. For the single-particle state functions, two different periodic expansions were used. We obtained the behavior of the ground-state energy per particle, the coupling parameter Γ, the particle localization, and the density of states as functions of the interparticle distance ${\mathit{r}}_{\mathit{s}}$.

In this paper we point out that for the confined states discussed recently for the phase associated with a stationary pattern, a conservation law for both the phase variation and the local wave vector exists. We discuss the physical implications of this observation as a function of the imposed boundary conditions. We investigate the influence of noise and we find that for the phase change and for the local wave vector, the stationary solution of the associated functional differential Fokker-Planck equation can be explicitly given.

The evaluation of thermodynamic properties of liquid alkali metals is reexamined in the approach based on the Gibbs-Bogoliubov inequality and using the fluid of charged hard spheres in the mean-spherical approximation as reference system, with a view to achieving consistency with the liquid structure factor. The perturbative variational calculation of the Helmholtz free energy is based on an ab initio and highly reliable nonlocal pseudopotential. Only limited improvement is found in the calculated thermodynamic functions, even when full advantage is taken of the two variational parameters inherent in this approach. The role of thermodynamic self-consistency between the equations of state of the reference fluid derived from the routes of the internal energy and of the virial theorem is then discussed, using previous results by Ho?ye and Stell [J. Chem. Phys. 67, 439 (1977)]. An approximate evaluation of the corresponding contribution to the free energy of liquid alkali metals yields appreciable improvement in both the thermodynamic functions and the liquid structure factor. It thus appears that an accurate treatment of thermodynamic self-consistency in the charged-hard-sphere system may help to resolve some of the difficulties that are commonly met in the evaluation of thermodynamic and structural properties of liquid metals.

The onset of convection in a rotating fluid layer heated from below is studied when the rotation speed is sinusoidally modulated. We study the instability that, in the absence of modulation, leads to stationary convection. We show that under modulation the conduction state can be stabilized or destabilized depending on the Taylor number, that the instability can be forward or backward for a range of Taylor numbers and modulation amplitudes, and that the critical Taylor number for the Küppers-Lortz instability is lowered. The calculations are carried out in the limit of large Prandtl number.

We studied, within Landau theory, the effect of preferential wetting on a binary-mixture film close to its consolute point. We evaluated the Fourier transform of the generalized susceptibility ${\mathrm{\chi }}_{\mathit{q}}$ as a function of the reduced temperature t, momentum transfer q, surface chemical potential ${\mathit{h}}_1$, bulk chemical potential h, and the film thickness L. As is well known, this quantity is readily determined by light-scattering experiments. Under the assumption that L≫${\xi }_{\mathit{B}}$, where ${\xi }_{\mathit{B}}$ is the bulk correlation length, we introduced a wall-wall decoupling approximation that allowed us to derive a simple analytic expression for ${\mathrm{\chi }}_{\mathit{q}}$. Our result exhibits classical scaling behavior and is shown to be valid for all strengths of the preferential wetting field ${\mathit{h}}_1$. Corrections due to wall-wall coupling are calculated in perturbation theory. We conclude that our result should not hold at the (shifted) critical point, for which the wall-decoupling approximation breaks down. In spite of this, however, we estimate that range of validity of our result is t≥${10}^{\mathrm{-}6}$ and L≥1 μm, corresponding to the present experimental resolution. The main conclusion is that, within this region, wetting always produces a suppression effect on the scattered light intensity, as compared to the nonwetting standard Ornstein-Zernike result.

The screened electrostatic potential and free energy of electric double layers near modulated boundaries are computed in terms of the height function h of the surface, as an extension of linearized Gouy-Chapman theory. Two approaches, one perturbative, the other iterative, are explored and compared, both expressing the average electrostatic potential away from the surface as a power series involving n-point correlations of h. When compared order by order in powers of the height function, the two methods are found to be equivalent, but they differ in the degree of differentiability demanded of h for a convergent expansion, the perturbative technique requiring infinite differentiability, and the iterative method needing only twice-differentiable functions. The wider applicability of the iterative method is shown to arise from the summation of certain infinite classes of terms in the perturbative expansion which remove ultraviolet divergences associated with the high-order nondifferentiability of the height function. The electrostatic free energy of interacting double layers is found to depend on height-height correlations both within and between the surfaces, a result that may also be interpreted as expressing the coefficients of capacity and induction of conductors in terms of their surface roughness. For boundaries with a well-defined modulation wavelength, the thermodynamic and electrostatic quantities are computed perturbatively in terms of the ratio of the modulation amplitude to the Debye-Hückel screening length, and the characteristic gradients of the height function. It is suggested that these long-wavelength results may find application in the study of the stability and structure of multilamellar liquid crystals composed of modulated membranes.

We present a new approach for the calculation of the dielectric response functions for various strongly coupled Coulomb systems, whose main common feature is that the charges are quasilocalized. Such a model is expected to be a valid description of a strongly coupled plasma in the Γ≫1 limit. The dielectric function ε(kω) and the longitudinal plasmon dispersion ω(k) appear as functionals of the equilibrium pair-correlation functions. We derive the longitudinal-plasmon dispersions for arbitrary k values for the three- and two-dimensional one-component plasmas; both of them saturate after an oscillatory behavior substantially below their random-phase approximation value for large k values. In two-component systems correlational effects bring about marked upward and downward shifts in the plasma frequency ω(k=0). We find good agreement with molecular-dynamics data for ${\mathrm{H}}^{+}$-${\mathrm{H}}^{2+}$ mixtures and predict a more significant shift for ${\mathrm{H}}^{+}$–high-Z mixtures.

In a bipolar birefringent nonlinear medium, such as nematic liquid crystals, stationary degenerate two-wave mixing between a weak probe beam and a strong pump beam can occur. This leads to strong amplification of the probe beam. In our analytical calculations, the general conditions for observing these effects and specific conditions pertaining to nematic liquid crystals are explicitly described.

We present the wavelet transform as a natural tool for characterizing the geometrical complexity of numerical and experimental two-dimensional fractal aggregates. We illustrate the efficiency of this ‘‘mathematical microscope’’ to reveal the construction rule of self-similar snowflake fractals and to capture the local scaling properties of multifractal aggregates through the determination of local pointwise dimensions α(x). We apply the wavelet transform to small-mass (M≲5×${10}^4$ particles) Witten and Sander diffusion-limited aggregates that are found to be globally self-similar with a unique scaling exponent α(x)=1.60±0.02. We reproduce this analysis for experimental two-dimensional copper electrodeposition clusters; in the limit of small ionic concentration and small current, these clusters are globally self-similar with a unique scaling exponent α(x)=1.63±0.03. These results strongly suggest that in this limit the electrodeposition growth mechanism is governed by the two-dimensional diffusion-limited aggregation process.

We introduce a simple dynamical model of cluster-cluster aggregation in which the diffusivity of a cluster depends on its position relative to its neighboring clusters. We demonstrate in one dimension that subjecting the cluster to a force inversely proportional to the distance between them can effectively offset the position-dependent drifts introduced by the position-dependent diffusivities. We present simulation results and also indicate how this model may be extended to study aggregation of interacting particles.

In this paper, we present a particle-cluster model for fractal aggregation. Using the current model, we investigate the properties of fractal aggregation in two dimensions in external fields and propose an argument on the threshold value in fractal aggregation. Our computer-simulation results show that the threshold value concentration is ${\mathit{P}}_{\mathit{c}}^{\mathit{a}}$=0.83±0.03 and fractal dimension ${\mathit{D}}_{\mathit{c}}$=1.67±0.07 at this concentration, which is in good agreement with experimental results.

The random-phase approximation (RPA) in Q-P representation is introduced. It is shown that the RPA equations can be regained from varying the ratio of energy-weighted moments ${\mathit{m}}_3$(Q)/${\mathit{m}}_1$(Q) with respect to the particle-hole operator Q. In particular, a restricted set of local operators Q(r) is discussed, leading to a hydrodynamic approximation to the RPA. The practical solution of the collective eigenvalue problem for a given multipolarity proceeds via a power expansion of Q(r) and the solution of a secular equation for coupled modes. As an application of our method, we discuss collective dipole vibrations (plasmons) in small spherical metal clusters.

The time-resolved x-ray emission is measured from spherical targets consisting of glass shells overcoated with plastic in which thin signature layers are embedded. These targets are illuminated at 351 nm by the 24-beam OMEGA laser system at the Laboratory for Laser Energetics of the University of Rochester. We measure a large burnthrough rate for bare plastic targets that can only be replicated in one-dimensional hydrodynamic simulations with laser intensities in excess of ten times the nominal intensity. We observe that the burnthrough times are affected by the presence of a thin outer coating (barrier layer). The burnthrough times depend strongly on the barrier-layer material and thickness, whereas one-dimensional simulation results predict only a small effect. Several processes are considered to explain these results: illumination nonuniformity, early shinethrough of the laser light through the plastic, prepulses, filamentation, self-focusing of hot spots, and the Rayleigh-Taylor instability. We conclude that mixing due to the Rayleigh-Taylor instability, enhanced by early shinethrough, is the most probable cause of the observed large burnthrough rates.

We report absolute photoemission cross sections and appearance potentials for the most intense ultraviolet emissions produced by electron-impact dissociation of boron trichloride, ${\mathrm{BCl}}_3$. The emission features studied include two atomic boron emissions, the 2${\mathit{p}}^2$ ${}_{}{}^2{}_{}{}^{}$D→2p ${}_{}{}^2{}_{}{}^{}$P° line at 208.9 nm and the 3s ${}_{}{}^2{}_{}{}^{}$S→2p ${}_{}{}^2{}_{}{}^{}$P ° line at 249.8 nm, which is the strongest ultraviolet emission feature, as well as the BCl ${\mathit{A}}^1$Π→X ${}_{}{}^1{}_{}{}^{}$ ${\mathrm{\Sigma }}^{+}$ system centered at 272.4 nm, whose previously reported cross section had to be revised upward by about 20% to 3×${10}^{\mathrm{-}18}$ ${\mathrm{cm}}^2$ at 40 eV. The 249.8-nm boron line was found to have the largest emission cross section with a value of 5.4×${10}^{\mathrm{-}18}$ ${\mathrm{cm}}^2$ at 75 eV. All cross sections displayed a prominent double onset structure with the second onset roughly 13 eV above the first one, which is very close to the ionization energy of atomic chlorine. This indicates the presence of a strong channel producing excited-state boron or boron chloride fragments simultaneously with ground-state chlorine ions. An attempt has been made to separate this ‘‘ionic’’ channel from the ‘‘neutral’’ channel in which neutral ground-state atoms are the only by-products accompanying the formation of the excited fragments.

The photon energy distributions of the first three resonance lines of heliumlike argon broadened by the local fields of both ions and electrons are calculated for dense H, D, or T plasmas containing small amounts of argon. The electron collisions are treated by an impact theory allowing for both widths and shifts in the distorted-wave approximation to all significant orders of the multipole expansion for the electron-radiator interaction. Ion effects are treated in the quasistatic approximation for dipole interactions between ions and radiators. These interactions between states of a given principal quantum number are calculated in the intermediate-coupling representation, using ion-field-strength distribution functions calculated by Boercker with the method of Iglesias et al [Phys. Rev. A 28, 1667 (1983)]. The profiles obtained were corrected for thermal Doppler broadening and also for ion-dynamical effects according to Stamm et al. [Phys. Rev. A 34, 4144 (1986)].

A recently developed Mössbauer instrument has been used to study the liquid dynamics of pentadecane at various temperatures and scattering angles. Widths of the quasielastic signal extracted from the data ranged between 16 GHz (at 12 °C) and 48 GHz (at 74 °C) at a scattering vector of 1.15 A${\mathrm{̊}}^{\mathrm{-}1}$. Similar measurements at five different scattering angles (at 12 °C) were also taken to investigate the Q dependence between 0.82 and 1.56 A${\mathrm{̊}}^{\mathrm{-}1}$. The results obtained are in good agreement with classical theory for coherent scattering from liquids.

Strong correlations between electrons and ions in hydrogen plasmas near metal-insulator boundaries are analyzed through an integral equation approach, which adopts the hypernetted-chain (HNC) approximation for the classical ion-ion correlation and the modified convolution approximation (MCA) for the quantum-mechanical electron-electron and electron-ion correlations. The resulting HNC MCA equations are solved self-consistently. The correlation functions and the equation of state thus calculated reveal the emergence of ‘‘Rydberg states’’ in the metallic phase near the metal-insulator boundaries, which acts to reduce the electric and thermal conductivities. Parametrized formulas for the equation of state and the conductivities are presented.