We have extended a recent perturbation theory [J. Chem. Phys. 82, 414 (1985); 84, 4547 (1986)] for nonionic systems to the one-component plasma (OCP). Characteristic features of the theory are its ability to handle both fluids and solids and the use of a reference potential whose repulsive range shrinks with density. Based on the computed thermodynamic data, we have developed a simple alternative (optimized hard-sphere) model, whose Helmholtz free energy is a sum of the Helmholtz free energy of the hard-sphere reference system and the Madelung energy of a fcc lattice. Comparison with available Monte Carlo and other theoretical results shows that the optimized hard-sphere model gives reliable solid (fcc) and fluid properties. The theory predicts that the fcc solid will melt at the Coulomb coupling parameter ${\Gamma }_m$=208 versus Helfer et al.’s [J. Stat. Phys. 37, 577 (1984)] Monte Carlo value of 196. This difference is due to a small difference (0.1%) in the computed excess free energy. The computed internal energy can be accurately fitted by an analytic form. Its two leading terms (for the fluid) are -0.899488Γ+1.272 97${\mathrm{\Gamma }}^{1/4}$, in close agreement with Slattery et al.’s [Phys. Rev. A 21, 2087 (1980); 26, 2255 (1982)] empirical fit to their Monte Carlo data. We conclude that the hard-sphere perturbation theory is applicable to a long-range repulsive system, such as the OCP, so long as the hard-sphere diameter is judiciously chosen by using a density-dependent reference potential.

We investigate currents of heat, concentration, and mass in binary fluid layers heated from below. In particular, we investigate traveling waves (TW’s) of laterally propagating convective roll patterns. We present nonlinear analytical TW solutions of a simple Galerkin model for impermeable horizontal boundary conditions. Bifurcation properties, stability, existence range, and the spatial field profiles of TW’s are determined for negative and positive separation ratios. The temperature wave lags behind and the concentration wave runs ahead of the wave in the vertical velocity. These phase differences imply time-independent global currents: in the upper half of the layer there is a lateral heat flow opposite to the TW and concentration flows parallel to it and vice versa in the lower half of the layer. Depending on where passive marked particles are injected they move together with a TW, or slower, or even backwards without there being a finite net mass transport. Finally we investigate whether the Reynolds stresses of a TW induce a mean lateral fluid flow.

Linewidths of the 5419-Å line are measured in a conventional shock tube. The Stark effect is the dominant broadening mechanism. Electron densities vary through the range 2.8×${10}^{16}$–2.2×${10}^{17}$ ${\mathrm{cm}}^{\mathrm{-}3}$, and temperatures vary from 8300 to 16 000 K. The Stark parameter increases by a factor of 2 as the temperature decreases. Results are compared with previous experimental data and semiempirical calculations.

Nonlinear particle dynamics are investigated in periodic, localized electrostatic fields which model a solution to the Zakharov equations. A large increase in the electron heating rates is observed and related to the partial destruction of the ponderomotive potential well. The threshold fields, for the increase in heating, are estimated from the overlap criterion and the analytical map which approximates motion of particles in the vicinity of the separatrix of the ponderomotive potential. Evolution of the distribution function and the averaged kinetic energy are also investigated.

The x-ray radiation generated in gold cavities (diameter 250–1000 μm) that were heated by 300-ps laser light pulses with a wavelength of 1.3 or 0.44 μm has been experimentally investigated. The absorbed laser intensity, averaged over the inner surface of the cavity, was varied in the range 2×${10}^{12}$–5×${10}^{13}$ W ${\mathrm{cm}}^{\mathrm{-}2}$. Laser light absorption was measured with an Ulbricht box. The cavity heating process was investigated by x-ray pinhole photography and time-resolved optical shadow- graphy. The radiant energy flux in the cavity and its spectral distribution were measured at three different locations in the cavity by spatially resolving transmission grating spectrometers. The experiments performed at the wavelength of 1.3 μm show low (∼30%) laser light absorption, delocalized heating due to refraction of laser light, and hard x-ray emission due to fast electron generation in the cavity. The 0.44-μm experiments show >80% absorption, localized heating at the laser-irradiated back wall of the cavity, and comparatively low hard x-ray emission. A maximum brightness temperature of 1.5×${10}^6$ K was measured in the smallest cavities.

Results are presented from experiments aiming at the study of the process of thermalization and confinement of the laser energy in closed geometry targets. The interior of spherical gold cavities (0.3–1.0 mm in diameter) has been irradiated with 300-ps pulses at average laser fluxes between 2×${10}^{12}$ and 5×${10}^{13}$ W/${\mathrm{cm}}^2$. A systematic study has been performed at 1.3- and 0.44-μm laser wavelength. The time-resolved x-ray spectrum of the radiation emitted by the cavities shows a double pulse structure. Furthermore, for λ=1.3 μm and during the second emission burst, M-band emission is observed. Analysis supports the hypothesis that, while the first burst emanates from the indirectly heated wall element, the second burst is due to expanding coronal plasma. Measurements showed that more favorable conditions can be achieved for λ=0.44 μm and deleterious effects like plasma filling and entrance hole closure can be avoided.

Radiation confinement in laser-heated gold cavities is analyzed on the basis of self-similar solutions of the hydrodynamic equations. The analysis is extended to include radiation losses through holes in the cavity. The possibility that a conversion layer on the inner wall of the cavity contributes to the measured radiation is also taken into account. The comparison with experiments performed at laser wavelengths of 0.44 and 1.3 μm with the Asterix iodine laser shows reasonable agreement with the theoretical predictions. The major difficulty in the comparison is the lack of detailed information about the conversion of laser light into x rays, especially in the 1.3-μm experiments.

We present a theoretical calculation of electron correlations in quantum and classical plasmas in a layered structure. This treatment rests on the solution of the first member of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy and the fluctuation-dissipation theorem. For arbitrary wave number this leads to a set of coupled integral equations which has to be solved self-consistently. In the long-wavelength limit it is found that the phase velocity of the collective excitation is renormalized due to short-range correlations. Our result is an extension of the earlier theory of K. S. Singwi et al. [Phys. Rev. 176, 589 (1968)] for bulk plasmas to the case of a layered electron gas. Our numerical results show that the correlation function for a layered structure is an oscillatory function of the lattice period, which reflects the interference between the density fluctuations in different layers.

There is a fundamental limit to the resolution that can be achieved in liquid-argon and liquid-xenon ionization detectors due to statistical fluctuations in the rate of charge collection along the track of a primary particle. The limit is typically much larger than the resolution expected from Poisson statistics. We present resolution data in both argon and xenon, a model to describe the data, and a discussion of how the model parameters can be manipulated in order to achieve even greater resolution.

A simplified version of the density-functional theory of Dharma-wardana and Perrot is introduced in which the Kohn-Sham-Schrödinger equation for the electrons is replaced by the Thomas-Fermi (TF) statistical approximation, while interionic correlations are still treated classically in the hypernetted-chain (HNC) approximation. The nonlinear TF and HNC equations are coupled by a defining relation for the effective ion-ion interaction potential. The resulting TF HNC theory smoothly interpolates between the Debye-Hückel and confined-atom TF theories. It is easily solved in the strong-coupling regime, while for weak and intermediate couplings it agrees well with solutions of the more elaborate density-functional theories for both ion distributions and effective potentials. We have found that the computer code solving our model does not converge in certain areas of ρ-T space, but at present we can only speculate as to the significance, if any, of this fact.

An electric polarization model for molecular liquids is proposed. This model is applied to liquid carbon disulphide in intense far-infrared laser fields. Changes in the liquid structure, in various time-dependent correlation functions, and in the dielectric properties of the optical medium are investigated. These changes are most profound at frequencies near the rotational resonance. When the perturbation is very strong, the molecular liquid becomes anisotropic and its polarization is saturated.

The surface structure of the AOT (sodium di-2-ethylsulfosuccinate) microemulsion system with equal volume fractions of ${\mathrm{D}}_2$O and decane, for AOT volume fractions of 0.42, 0.305, and 0.181, has been studied by a combination of x-ray specular reflectivity and scattering from the bulk. Scattering from the bulk material below the surface is consistent with Kotlarchyk’s interpretation of densely packed spherical micelles. Specular reflectivity from the surface implies a surface electron-density profile consistent with one to two layers of microemulsion droplets. The size of and distance between droplets is consistent with the respective values for the droplets in the bulk phase.

The Kosterlitz-Thouless-Halperin-Nelson-Young theory of melting is applied to a two-dimensional charged colloidal crystal. The renormalization of elastic constants due to anharmonic and dislocation pair-screening effects is calculated. For colloidal spheres (‘‘polyballs’’) suspended in a thin film of water confined between two glass plates whose surfaces are highly charged, as in recent experimental configurations, the corrections to the harmonic results simply require an altered effective polyball charge to reproduce virtually the identical melting curve of the harmonic approximation (which agrees well with experiment). The effect on the melting curve of added salt is also calculated; the corresponding experiments have yet to be performed. For a film between uncharged surfaces the anharmonic correction again softens the lattice significantly. Dislocation pair screening causes an additional but minor reduction of the elastic constants. Neither correction eliminates a nonmelting behavior characteristic of the two-dimensional screened Coulomb system in this configuration.

The frequency and temperature dependence of the complex dielectric constant was measured near the smectic-$C^{\mathrm{*}}$–smectic-A liquid-crystal phase (Sm-$C^{\mathrm{*}}$–Sm-A) transition for two ferroelectric liquid crystals with a very large spontaneous polarization. The dielectric strengths as well as the corresponding relaxation frequencies of the dielectric modes were determined. Due to the large polarization we were able to resolve the contributions from the soft mode and the Goldstone mode in a comparatively large temperature interval in the Sm-$C^{\mathrm{*}}$ phase close to the transition to the Sm-A phase. In the Sm-A phase, the relaxation frequency and the inverse dielectric strength of the soft mode decrease linearly when approaching $T_c$. Comparing the experimental data with a recent theoretical calculation of the complex dielectric constant, we conclude that we have a fairly good understanding of the behavior of the complex dielectric constant in the whole Sm-$C^{\mathrm{*}}$–Sm-A transition range.

We present an exact new model of branched polymers of even functionality. Surprisingly, our model belongs to the universality class of the O(n) model where n is the activity for loops: Branchings do not affect the universality class and the upper critical dimension is 4. However, in the dilute limit, the model undergoes a first-order transition. These results are contrary to current belief.

We describe a simple method based on the hypervirial theorem along with a second-quantization formalism, which allows us to obtain recursion relations without using explicit wave functions for the calculation of matrix elements such as {exp[-a(r-$r_e$${\left)\right]\mathrm{\}}}^n$, (r-$r_e$${)}^n$, (r-$r_e$${)}^n$exp[-a(r-$r_e$)], and {exp[-a(r-$r_e$${\left)\right]\mathrm{\}}}^n$(d/dr) for the rotating Morse oscillator.

A three-dimensional stochastic process which has the particle density as its probability density is constructed from Nelson’s stochastic mechanics, yielding a particle trajectory picture for density-functional theory. This diffusion process enables simulating the detailed behavior of multiparticle quantum systems with substantial computational economy. A stochastic-mechanical form of the Heisenberg uncertainty principle holds in the new context. Moreover, a kinetic energy functional is defined and shown to be connected with other kinetic energy expressions, and in the case of a time-independent ground state a formal dynamics for the process is proposed. A related real-space version is developed of Bohm’s quantum potential formalism.

In order to examine dynamic aspects, including excitations, in α-helix structures in proteins, models in three spatial dimensions of α helices have been set up and their dynamic behavior examined by numerical computations. The potential-energy function describing the system is based on empirical data and implemented in the molecular-dynamics computer program charmm. Two types of excitations have been examined: lattice vibrations and intramolecular vibrations. The former disperse rapidly while the latter (being essentially amide-I-type vibrations) evolve regularly. A simple model based on a system of coupled linear oscillators can reproduce the time evolution of the intramolecular vibrations.

The electrical response of porous electrodes is calculated in several particular cases, which permit one to approach the response of a realistic model for a porous interface. The case of nonblocking surfaces and the case of the diffusion impedance of a fractal electrode are also considered. The use of Bode diagrams is shown to provide a very simple means for calculating phase angles and algebraic values for the impedance. It is demonstrated that for a blocking deterministic Sierpiński electrode the impedance presents oscillations around a constant phase angle (CPA). Various electrochemical regimes (blocking, nonblocking, and diffusive) are considered, giving rise to a variety of exponents. For blocking electrodes it is shown that at a given frequency, the power is dissipated in certain parts of the electrodes having a characteristic size which is a direct function of frequency. The fact that the response of the system is linear permits one to relate in general the dc response to the phase angle in the blocking regime and to study certain diffusive cases. It also permits one to deal with cases very common practically where the response of a flat surface would itself exhibit a CPA. In the case of a pure diffusion impedance the response is shown to be related directly to the Minkowski-Bouligand exterior dimension of the interface through the exponent (D-1)/2. This approach can be generalized to any type of irregular electrode independently of its fractal character. If both diffusion and Faradaic (electrochemical) impedance play a role, a CPA response exists for a porous electrode with an exponent equal to D-2. We discuss various regimes in which diffusion plays a role together with Faradaic, resistive, and capacitive effects. It is shown that there is in general no relation between fractal dimension and constant phase angle except in the case of diffusion. The response of irregular electrodes is shown to be related to the fractal dimension when the electrochemical regime is local.

A complete exact analysis of invariant Cantor sets in a piecewise linear but nontrivial area-preserving twist map is given. The results are based on concise formulas for minimizing periodic orbits, which in turn are derived from rigorous work by Aubry and Percival using only fundamental relations of continued-fraction theory. The exponential law for the decay of Cantori gaps, however, is found from the mapping itself with the aid of an elementary argument. The general scheme determining the initial conditions is transformed in the case of noble Cantori to an equivalent dynamical system permitting superexponentially fast calculations. By constructing polygonal embeddings the fractal and Hausdorff dimension of the invariant sets considered is proved to be precisely zero under all circumstances. Thus most notions and generic properties of Cantori can be understood within the frame of an explicitly solved example.