In theoretical and experimental studies of high-frequency (${\omega }_{\mathrm{ci}}\ll \omega \lesssim {\omega }_{\mathrm{pi}}$) ion heating by electrostatic instabilities driven by a current perpendicular to both a density gradient and an external magnetic field, one instability is found to remain active for a current velocity smaller than the ion thermal velocity. For one experiment, the level of turbulence, effective ion collision frequency, and ion heating rate are also estimated.

Laminar interactions of plasmas of different mass and density, streaming transverse to a magnetic field, are described theoretically and by computer simulation. Piston-ion dynamics yield new solutions not found in single fluid problems.

We derive a statistical mechanical expression for the surface tension of a liquid-vapor interface. It contains the density profile and the direct correlation function in the vicinity of the interface. When a local Ornstein-Zernike approximation is made on the direct correlation function, the surface-tension theory of Fisk and Widom is obtained.

Shortly after initiation of a high-voltage toroidal discharge in Ar, departure from free-electron acceleration is observed, together with electron heating such that the total energy input is accounted for. This early behavior is attributed to a high-frequency instability (${\omega }_{\mathrm{pi}}<\omega <{\omega }_{\mathrm{pe}}$) due to interaction between relatively few trapped electrons and the streaming electrons.

The self-stabilization of the two-ion-beam instability due to microturbulent ion heating has been measured in a plasma with variable temperature ratio ($2.0<\mathrm{}\frac{T_e}{T_i}<10.0\mathrm{}$). When the plasma is unstable, excited ion waves and background microturbulence are observed to grow, saturate, and damp, in conjunction with ion heating. When the plasma is stable, no ion heating is observed. The ion heating $e$-folding length is $\approx 500{\lambda }_{\mathrm{de}}$. This heating may occur in the formation of collisionless shocks.

A criterion is developed for the Anderson localization of the one-magnon excitation in a substitutionally disordered two-sublayer Heisenberg antiferromagnet. Assuming nearest-neighbor exchange interactions, application is made to $\mathrm{K}\left({\mathrm{Mn}}_{1-c}{\mathrm{Co}}_c\right){\mathrm{F}}_3$ near zero temperature. Taking, for simplicity, $J^{\mathrm{M}\mathrm{n}-\mathrm{C}\mathrm{o}}={\left(J^{\mathrm{Mn}}{J}^{\mathrm{Co}}\right)}^{\frac{1}{2}}$, a critical condition for localization is found for all impurity concentrations, yielding good agreement with recent experiments.

A microscopic model is presented for the structure and superconductivity of $A_x{T}_{1+y}{C}_2$ compounds, where $A$ is a monovalent atom or radical, $T$ is an even-valence transition metal, $C$ is a chalcogenide, and the parameters $x$ and $y$ lie in the ranges $0.1<x\lesssim 0.3$, $0<~y\lesssim 0.5$. The model explains why the maximum superconducting transition temperature ${T_S}^{max}$ is higher than 12°K in bridge compounds with $y=0.1\mathrm{}$, although the maximum value of $T_S$ observed in related layer compounds with $y=0.0\mathrm{}$ is about 6°K.

We report the observation of electron tunneling between two metal electrodes separated by an amorphous germanium layer. Measurements of the derivative of the conductance with respect to the applied voltage yield the tunneling phonon density of states for amorphous germanium.

We present an augmented-plane-wave pseudopotential calculation of the scattering of quasiparticle excitations by thermal phonons in symmetry zones of the Fermi surface of copper. The results provide an interpretation of recent experimental data.

We consider the self-induced transparency in semiconductor crystals and find that it is possible for a pulse whose carrier frequency lies below the plasma frequency to propagate through the crystal. The phenomenon is caused by a local intensity-dependent depression of the plasma frequency.

It is shown that the theory of localization developed by Economou and Cohen together with the coherent-potential approximation can be used to describe the magnetic excitations in substitutionally disordered antiferromagnets. The results are in good agreement with recently published experimental data.

The small-angle scattering of ${\pi }^{+}$ from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ was measured at 115, 167, and 242 MeV. The measurements covered the Coulomb-nuclear interference region from 3° to 10°. The real part of the forward nuclear amplitude was extracted from the data.

A recent experiment has shown us that the Goos-Hänchen shift is quantized, the eigen-functions being the transverse electric and magnetic modes. We give here a straightforward theory of this phenomenon, together with the prediction that our new transverse shift is also quantized, with the circularly polarized modes inside the evanescent wave as eigenfunctions. An experimental test of the latter point is being considered.

For a class of model quantum field theories in two-dimensional space-time describing a neutral scalar boson field interacting in a region of length $l$, the vacuum energy density converges as $l\to \infty$. In the same limit the vacuum state approaches zero in the weak sense, as proposed by van Hove.

We investigated the missing-mass spectra at the $2\pi$ threshold in the reaction $p+d\to {\mathrm{He}}^3+X^0$ and searched for the resonance reported at a mass of 450 MeV using 2-GeV protons. The shape of the missing-mass spectra below the ${\eta }^0$ mass deviates from two-body phase space and was similar to that obtained with 3-GeV protons. If a 450-MeV resonance exists, the c.m. cross section for producing it in this reaction is less than 10.8 × ${10}^{-36\mathrm{}}$ and 5.7 × ${10}^{-36\mathrm{}}$ ${\mathrm{cm}}^2$/sr with 2- and 3-GeV protons, respectively.

Analysis of ${\pi }^0$, ${\eta }^0$, and ${\omega }^0$ production by 2- and 3-GeV protons in the reaction $p+d\to {\mathrm{He}}^3+X^0$ leads to an understanding of the variation of these cross sections with respect to momentum transfer and yields information concerning the ${\mathrm{He}}^3$ form factor. It is shown that the observed missing-mass spectra at the $2\pi$ threshold, which deviates from phase space in this reaction (the ABC effect), can be explained using this momentum-transfer dependence of the ${\mathrm{He}}^3$ form factor.

The decay $\Lambda \mathrm{}\left(1520\right)\mathrm{}\to \Sigma \mathrm{}\left(1385\right)\mathrm{}\pi$ has been studied in an energy-independent partial-wave analysis of the reaction $K^{-}p\to \Lambda {\pi }^{+}{\pi }^{-}$ in the momentum range 300 to 470 MeV/c. The width is found to be $\Gamma =1.40\mathrm{}\pm 0.26$ MeV. Combining this result with one recently reported for $\Lambda \mathrm{}\left(1690\right)\mathrm{}$, we obtain a singlet-octet mixing angle $\left|\theta \right|=73\mathrm{}°\pm 10°$, in disagreement with the value $\theta =-25\mathrm{}°\pm 6°$ derived from the two-body decays of the $J^P={\frac{3}{2}}^{-}$ states.

A short-lived resonant state with configuration ${\mathrm{}\left(2s\right)\mathrm{}}^2\mathrm{}\left(2p\right)\mathrm{}$ ${}_{}{}^2{}_{}{}^{}P_{}^o{}_{}{}^{}$ is computed for ${\mathrm{H}}^{--}$ using the stabilization method. The resonant energy is 14.8 eV and the estimated width is roughly 1 eV, all in excellent agreement with experiment.

A generalized many-electron pseudopotential approach is presented for electron-neutral-atom scattering problems. A calculation based on this formulation is carried out for the singlet $s$-wave and $p$-wave electron-hydrogen phase shifts with excellent results. We compare the method with other approaches as well as discuss its applications for inelastic and rearrangement collision problems.

Experimental results are reported which conclusively show that diatomic molecular helium ions recombine dissociatively with electrons. It is shown that dissociative recombination accounts for at least half of the total electronic recombination of ${\mathrm{He}}_2^{+}$ at a temperature of 300°K and in the pressure range from 15 to 55 Torr. The experimental technique which was used in this work includes measurement of the perturbation of the $2{}_{}{}^3{}_{}{}^{}S$ metastable density which results from a time-dependent perturbation of the electronic recombination coefficient.