The effect of resonant collisions resulting from (Coulomb) dipole-dipole interaction is examined on optical bistability in the mean-field approximation. A propagator formulation is employed. A generalization of the standard equations of state for the absorptive-dispersive bistability is obtained. It is found that Lorentz-Lorenz local-field correction produces a small but appreciable shift of the optical-phase-transition point.

We report a set of neutron spectrum measurements made at the Alcator-$C$ tokamak under Ohmic-heating conditions. It has been found that the width of the D-D fusion neutron peak increases with the plasma ion temperature consistent with the theoretical prediction. In particular, the neutron spectra resulting from the sum of many plasma discharges with ion temperatures of 780 and 1050 eV have been obtained. The width for the 780-eV case is ${64}_{-11\mathrm{}}^{+ 9}$ keV and that of the 1050-eV case, ${81}_{-14\mathrm{}}^{+10\mathrm{}}$ keV (full width at half maximum), corresponding to ion temperatures of 740 and 1190 eV, respectively.

It is shown that the combined effect of resistivity, viscosity, and thermal conductivity leads to large-scale stationary convection. This is done for a cylindrical current-carrying plasma in a shearless magnetic field. Convection is shown to take place for large wave numbers and $\frac{B_{\theta }}{B_z}\gg 1$.

The electrostatic dispersion and instabilities for an anisotropic relativistic plasma stream are analytically studied for various regimes with streaming dissipation relevant to the analysis of fusion and turbulence in beam-plasma and wave-plasma interaction. It reveals the modified spectrum of streaming dispersion and onset of instability at nonrelativistic temperatures suitable for space, at moderately relativistic temperature including fusion, and at ultrarelativistic temperature limit relevant to astrophysical plasmas and pulsars.

I have further developed a molecular-dynamics technique, based on the introduction of stochastic boundary conditions, which had been used previously to simulate stationary nonequilibrium states. By simulating two symmetrical thermal gradients, periodic boundary conditions can be used in all directions. In this way unphysical effects of the thermal walls, existing in the previous version of the technique, have been eliminated. The local equilibrium hypothesis has been verified throughout the whole region of the thermal gradient. The new technique seems suited to study the correlation of dynamical variables in stationary nonequilibrium states.

We investigate the dependence of Stark-broadened Lyman-$\beta$ lines emitted by ${\mathrm{Ne}}^{9+}$ and ${\mathrm{Ar}}^{17+}$ in protons, on the composition parameter $p=\frac{C_b}{(C_a+C_b)}$, given in terms of the plasma parameter $\Lambda$, emitter charge $Z_a$, and the relative concentrations $C_{a,b}=\frac{N_{a,b}}{(N_a+N_b)}$. We propose to use the very sensitive $p$ dependence of these lines around $p\sim 1$ to measure small quantities of heavy material contaminating the hydrogenic burn.

We comment on some statements and results in the paper by Beckman, Karsch, and Miller. We also point out certain anomalies in treating the zero-mass case with a constraint.

Recent measurements of the $5s$-subshell photoelectron angular distribution of xenon have found larger values for the asymmetry parameter $\beta$ in the region of the $5s$-subshell cross-section minimum than predicted by relativistic random-phase-approximation calculations. Final-state ionic configuration interaction is adduced as a possible explanation for this and other discrepancies.

A new infrared absorption feature in the low-temperature spectrum of solid ${\mathrm{D}}_2$ and ${\mathrm{H}}_2$ containing small amounts of tritium has been observed. The absorption can be interpreted as being due to electrons in bubblelike structures with diameters of approximately 9 Å.

For the nondispersive propagation of waves in one dimension, there is no essential difference between the concepts of longitudinal and temporal coherence, and these terms are often used interchangeably. For the dispersive propagation of waves, such as electrons or neutrons in vacuo, or light in a medium, this is no longer the case. We analyze the coherence properties of a dispersively propagating beam of radiation, and discuss the observation of its spatial and temporal coherence properties by means of a two-beam interferometer.

Multistable light amplifications and self-pulsations in a resonant-type semiconductor laser diode (LD) amplifier are predicted. A basic idea is derived from the active layer refractive index dependence on carrier density. An LD amplifier is shown to act as a high-$Q$ nonlinear Fabry-Perot interferometer with true optical gain and nonlinear refraction. Periodic and chaotic self-pulsations are shown to occur in the regime where the delay time of the feedback is smaller than the carrier lifetime.

A simple method of solving the electron-transport equation in the presence of a steadily ablating plasma is described. The results show that, compared with a motionless plasma, the presence of steady-state ablation can substantially reduce the electric field in the direction of the heat flow. It does not lead to further reduction of the (center-of-mass) heat flow.

The influence of anharmonic elastic terms on the hydrodynamics of discotic liquid crystals is examined. These terms generate a nonlinear coupling between the velocity field and thermally excited undulation modes which, it is shown, causes four of the five viscosities in these systems to diverge as ${\omega }^{-\frac{1}{2}}$ at small frequencies $\omega$. This implies that the attenuation of sound in these systems should scale as ${\omega }^{\frac{3}{2}}$ (not ${\omega }^2$ as in conventional materials). A simple relation between three of the diverging viscosities is found. Various experimental tests of these predictions are suggested.

The scalar and tensor polarizabilities of the barium $6snd$ ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ states with principal quantum number $n$ ranging from 14 to 30, as well as those of the $5d7d$ ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ perturber state near $n=26\mathrm{}$, have been measured with high-resolution laser-atomic-beam spectroscopy. The data are analyzed by calculating the contribution to the polarizabilities of all known odd-parity states connected via the electric dipole operator with the ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ states. In this way the contributions of the unknown $6snf$ ${}_{}{}^1{}_{}{}^{}F_3^{}{}_{}{}^{}$ states are inferred. The results indicate that the ${}_{}{}^1{}_{}{}^{}F_3^{}{}_{}{}^{}$ series is heavily affected by at least two perturber states. A tentative three-channel quantum-defect—theory analysis of the ${}_{}{}^1{}_{}{}^{}F_3^{}{}_{}{}^{}$ series, based on a fit to the experimental polarizabilities, is presented.

A systematic method for determining lower-bound energy functionals within both the density-functional and orbital frameworks is presented. Lower-bound calculations are carried out on the Thomas-Fermi-Dirac—$\frac{1}{5}$ von Weizsäcker ($\mathrm{TFD}\frac{1}{5}\mathrm{W}$) diatomic nitrogen molecule and the Hartree-Fock (HF) diatomic hydrogen molecule. In the $\mathrm{TFD}\frac{1}{5}\mathrm{W}$ model, binding is found but not as much as previously thought to exist. Furthermore, an anomaly in the behavior of the energy at short internuclear distances (∼1 bohr) is discovered through comparisons with HF data. In the Hartree-Fock theory, a strict lower bound on the ${\mathrm{H}}_2$ potential-energy curve is obtained without performing any two-electron integrals. A dissociation energy results, which is 6% more than the exact HF value.

The Fermi contact term of the nuclear-spin—spin coupling in the HD molecule is calculated using finite-field many-body perturbation theory (FF MBPT). The one-electron states are generated by the Hartree-Fock potential in the presence of the Fermi contact interaction. The procedure through third order in electron correlation gives a value for the Fermi contact term of 37.2 Hz in fair agreement with the best estimated value of 40.0 Hz at the equilibrium internuclear distance. The result suggests that the FF MBPT approach provides a highly efficient and systematic method for the calculation of the Fermi contact term. A possible origin of the general overestimate by the coupled Hartree-Fock method is also discussed.