The low-frequency microfield distributions obtained for dense ionic mixtures are used to compute the complete combined Stark and Doppler profiles of Lyman $\alpha$ and $\beta$ lines emitted by Ne X and Ar XVIII immersed in dense proton plasmas of interest for inertial-confinement fusion (ICF). Electron broadening is treated within the impact approximation. A certain emphasis is paid to the ion proportion effect, conveniently analyzed through $p=\frac{C_b}{(C_b+C_a)}$. A novel feature of the present calculation is afforded by the wings' behavior that is fully investigated analytically. For $\left|\Delta \nu \right|\ge 2$ Ry, the asymptotic profiles fall within 1% of the completely numerical ones (Doppler excluded). Excellent agreement with previous Tighe-Hooper calculations is achieved. Extensive numerical results are given for $V$ up to 0.8 (where the spectroscopy parameter $V$ is $\frac{r_0}{{\lambda }_{D_e}}$, the ratio between the classical radius of the electron and the electron Debye length).

The hydrodynamic equations for three-dimensional stacked hexatic liquid crystals, i.e., for hexatic-$B$ and its tilted analogs, smectic-$F$ and smectic-$I$, are presented. Differences and similarities to the hydrodynamics of smectic-$A$ and smectic-$C$ are discussed and the role of the additional variable characterizing the bond orientational order is elucidated.

We present molecular-dynamics results for a dense Lennard-Jones fluid near the triple point subjected to the Couette flow. The method is based on the introduction of stochastic boundary conditions to simulate the contact with a moving thermal wall. The method allows the simulation of bulk properties of the system and the study of the local thermodynamical equilibrium. Furthermore, it gives a physical description of momentum and heat transfer near a Couette wall. We found that the shear viscosity depends on shear rate near the triple point (breakdown of Newton's law) while for a point far from the liquid-solid coexistence line there is no appreciable deviation from Newton's law. In the bulk region, where boundary effects are negligible, we found that the local thermodynamical equilibrium holds for all simulated shear rates (up to 1.14± ${10}^{11}$ ${\sec }^{-1\mathrm{}}$). Moreover, we do not find any dependence on the number of particles used in the simulation. Last we compare the results for the shear-dependent shear viscosity with theoretical predictions for nonlinear behavior.

A local formulation of the Boltzmann $H$ theorem associated with the revised Enskog equation is presented. For weak spatial gradients, one can prove that the entropy production is positive. If we further restrict ourselves to near local equilibrium states, the entropy production takes the form of products of thermodynamic forces by fluxes, i.e., the Gibbs relation, and the entropy flux reduces to the heat flux divided by the temperature.

Temperature-dependent and Coulomb-like interactions taking into account short-ranged quantum effects are reviewed for nonrelativistic and hydrogenic pairs of pointlike charges of either sign in a high-temperature plasma with ions of arbitrary charge $Z$. A particular emphasis is given to the pseudopotential within a pair of electrons with parallel spins. Closed-form and accurate expressions are derived and compared with numerical values.

Debye-Hückel and ion-sphere plasma screening models have been used in a study of inelastic scattering of electrons by one-electron ions in dense, high-temperature plasmas. Cross sections for transitions among the $1s$, $2s$, and $2p$ states have been calculated using close-coupling and distorted-wave descriptions. The optically allowed $1s\to 2p$ and $2s\to 2p$ cross sections are substantially reduced at all energies by plasma screening of the long-range dipole coupling. The $1s\to 2s$ cross section is less sensitive to plasma effects. For an ion of nuclear charge $Z$, the scaled inelastic cross sections $Z^{4}Q$ are roughly independent of $Z$ for fixed values of $\frac{E}{Z^2}$ and $Z\Lambda$ or $Z{R}_z$, where $E$ is the electron's kinetic energy, $\Lambda$ is the Debye length, and $R_z$ is the ion-sphere radius.

An atomic analog to the molecular Rydberg-Klein-Rees inversion technique is proposed. It is shown that with this method atomic energy levels can be inverted directly to yield unique pseudopotential functions which describe the effective valence-electron-atomic-core interaction. When the energy levels can be accurately represented by a simplified quantum-defect formula, the inversion can be carried out analytically and, as a result, a new functional form for valence-electron pseudopotentials is presented.

An irreducible tensor expansion for the multipole interaction written in the product basis for the interacting atoms is used to derive an analogous expression in a coupled-angular-momentum basis. The result may be applied directly to a recent theory [Phys. Rev. A 22, 1848 (1980)] of coherences produced by radiatively assisted inelastic collisions.

Excitation transfers between the $4{}_{}{}^2{}_{}{}^{}D$ and $4{}_{}{}^2{}_{}{}^{}F$ states of lithium are studied in a temperature-controlled heat-pipe oven. These transfers are induced by collisions with Li, He, and Ar ground-state atoms. Quenching cross section and radiative rates are also measured. For the excitation transfer process, the thermally averaged cross sections are, respectively, ${\sigma }^{\mathrm{Li}}=400\mathrm{}$ ${\mathrm{\AA }}^2$, ${\sigma }^{\mathrm{He}}=120\mathrm{}$ ${\mathrm{\AA }}^2$, and ${\sigma }^{\mathrm{Ar}}=190\mathrm{}$ ${\mathrm{\AA }}^2$. These values agree with the experimental results of Gallagher in Na and the calculations of Gersten. Finally, the behavior of the $4{}_{}{}^2{}_{}{}^{}D-4\mathrm{}{}_{}{}^2{}_{}{}^{}F$ two-level system in the $l$-mixing regime is investigated in the case of Ar collisions.

A modification is proposed to the kinematical description of a binary-encounter collision, taking into account the $p$-dependent ($p$ is the initial momentum of the target electron) kinetic energy lost by the slow (ejected) electron while propagating out of the atomic potential. It is shown, at least for the high-energy asymmetric ($e$, $2e$) reaction on helium, that this correction leads to a "universal" representation of the data and to a remarkable agreement with experiment over a wide range of ejection energies and scattering angles.

By introducing the Doppler shift into Mollow's theory of saturated absorption and by performing the average over the velocity distribution, a Lamb-dip line shape is obtained. Analytical expressions and numerical results are presented. In some cases, these results do not agree with the results of the existing theory.

The applicability of Boltzmann's $H$ theorem based on a traditional choice of the positive semidefinite (Lyapunov) function in the characterization of the approach to steady state as described by a generalized master equation is addressed. In general it is found that such an application is not appropriate although there is an indirect application in a special case.

A dynamical theory of simple fluids which incorporates exactly all the effects of a single binary collision is used to study the dynamic structure factor $S(q,\omega )$ for Lennard-Jones fluids. The comparison of our results with those of recent neutron inelastic-coherent-scattering experiments of dense krypton gas indicates that $S(q,\omega )$ is sensitive to the details of the interatomic potential even in moderately dense gases.

In experiments involving deterministic chaotic signals, contamination by random noise is unavoidable. We discuss a practical method that disentangles the deterministic chaos from the random part. The method yields a characterization of the strange attractors together with an estimate of the size of random noise.

By use of a method due to Katriel, it is shown that the Levy formulation of the density-functional theory encompasses excited states.

We have performed variational calculations on the helium isoelectronic sequence for values of the nuclear charge $Z$ ranging from 1 to 10. The basis used is a modification of that employed by Frankowski and Pekeris in 1966, whose calculation has not been superseded before now. Using 230-term wave functions, we obtain for $Z=2\mathrm{}$ through 10 variational energies accurate to better than a few parts in ${10}^{13}$. Our results illustrate the importance of using basis functions which have the same analytic structure as the exact wave function being approximated.

Expressions for inverted cusps in electron spectra near zero velocity from inelastic ion-atom collisions are derived by the plane-wave Born approximation. In addition, it is shown that for $2p_0$ ionization not only the cusp-shaped electron-loss peak is inverted but the binary-encounter peak too.

The observation of structure in the photoionization cross section of magnesium in the vicinity of the $3s$ threshold is reported. The structure is the result of simultaneous (single photon) two-electron excitation followed by autoionization. The data are in excellent agreement with theory.

Experimental data of photoionization cross sections, photoelectron angular distributions, and photoelectron spin polarizations for mercury $5d$ have been used to determine dipole transition amplitudes and their relative phases. These basic quantities are compared with predictions of different theoretical models, revealing a strong interchannel interaction between the $5d\to \epsilon p$ and $5d\to \epsilon f$ channels, which was not directly visible in the measurable parameters.

A general expression for the change in transport coefficients of a dilute gas in the limit of an infinite external magnetic or electric field is derived without using a perturbation expansion of the collision operator. Previously derived properties of the saturated field effects are subsequently generalized and some implications are discussed.