We solve the steady-state coupling problem of lower-hybrid waves excited by a wave-guide array. The theory takes into account the ponderomotive density modulation to all orders in the electric field amplitude but assumes that the nonlinear effects are important only along the magnetic field lines. The important new feature is the appearance of a resonant term in the transverse refractive index, which is due to the finite size of the excitation structure. A calculation for two waveguides, linear density profile, and constant temperature is presented.

A double-target technique is used to measure the velocity-profile uniformity with which laser-irradiated thin-foil targets are ablatively accelerated. Studies of the effects of laser nonuniformities on the target acceleration reveal an increase in lateral smoothing with increasing laser intensity. Measurements of targets accelerated to velocities (160 km/sec) sufficient for pellet fusion implosions will be presented and discussed.

The temperature variation of the phase soliton density has been determined in ${\mathrm{Rb}}_2$Zn${\mathrm{Cl}}_4$ and a nonclassical critical exponent ½ has been found. Electron-paramagnetic-resonance and nuclear-magnetic-resonance data demonstrate that in ${\mathrm{K}}_2$Se${\mathrm{O}}_4$, ${\mathrm{Rb}}_2$Zn${\mathrm{Cl}}_4$, and ${\mathrm{Rb}}_2$Zn${\mathrm{Br}}_4$ the soliton width is large as compared to the intersoliton spacing over most of the incommensurate phase so that the continuum description is adequate.

A dilute $n\to 0$ vector model provides a useful description of equilibrium polymerization in a solvent. Such polymerization occurs in liquid sulfur solutions and leads to a lower critical solution point that is analogous to the tricritical point found in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixtures. In the mean-field approximation, the model is identical to an earlier theory of Scott. Nonclassical critical behavior can explain certain discrepancies between Scott's theory and experiment.

The optical constants of heavily doped silicon are determined between 1.5 and 4.1 eV with use of polarization modulation ellipsometry. For photon energies less than 3.4 eV it is found that there is a substantial increase in the optical absorption coefficient for As-doped silicon, but a much smaller increase for B-doped or P-doped silicon. It is believed that this is due to $d$-electron admixture into the conduction band when the dopant is As.

A novel dynamic Monte Carlo renormalization-group method is devised. Application to the kinetic Ising model in one dimension yields a value of $z$, the dynamic critical exponent, which is in excellent agreement with the exact result. In two dimensions we find $z=2.22\mathrm{}\pm 0.13$ with the most probable value $z=2.17\mathrm{}$.

Measurements of transient photoinduced optical absorption in $a$-${\mathrm{As}}_2$${\mathrm{Se}}_3$ show that carriers thermalize within a distribution of localized states in the band gap. Photocurrent as well as photoinduced optical absorption transients are explained in a unified way with the multiple-trapping mechanism. Under such circumstances, transient photoconductivity provides a spectroscopy of the density of localized states.

The width of the conduction- and valence-band tails in amorphous silicon hydride are inferred from time-of-flight measurements of the temperature dependence of the electron and hole drift mobilities, and a multiple-trapping model of dispersive transport.

Results on spin dynamics in CsNi${\mathrm{F}}_3$ with applied magnetic fields are obtained through a detailed study of the shape of a sharp near-infrared absorption line. In a rather extended field and temperature range, a universal curve connects the linewidth to the temperature when ${\mathrm{}\left(\mathrm{JH}\right)\mathrm{}}^{\frac{1}{2}}$ is used as an energy unit. The relevance of the reduced variable $\frac{k_{\mathrm{B}}T}{{\mathrm{}\left(\mathrm{JH}\right)\mathrm{}}^{\frac{1}{2}}}$ to the existence of solitons is discussed.

The depression of the superconducting transition temperature of lanthanum due to the presence of praseodymium impurities shows a pronounced maximum as a function of pressure at ≃230 kbar. We conclude that the $4f^2$ shell of Pr delocalizes under such high pressure and hence demagnetizes in analogy to the familiar case of the $4f^1$ configuration of Ce impurities in La at low pressure.

The $D^0\to {\overline{K}}^0\eta$ decay mode is shown to be suppressed by a large factor insensitive to $\eta -{\eta }^{\prime }$ mixing and SU(3)-symmetry breaking in all transitions via intermediate states with flavor quantum numbers of a $q\overline{q}$ pair, e.g., SU(3) octet, but to be roughly equal to the ${\overline{K}}^0{\pi }^0$ and ${\overline{K}}^0{\eta }^{\prime }$ when produced via exotic $\mathrm{qq}\overline{q}\overline{q}$ channels. The relative decay rates to ${\overline{K}}^0\eta$, ${\overline{K}}^0{\eta }^{\prime }$, and ${\overline{K}}^0{\pi }^0$ distinguish between models producing the additional $q\overline{q}$ pair in weak or strong vertices.

Upper bounds on the critical temperature are found in terms of the Higgs-boson mass in $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ and SU(2) ⊗ U(1) gauge theories. Also, an upper bound on the Higgs-boson mass as a function of the supercooling ratio is found, provided that quantum tunneling is not sufficient to complete the phase transition from a symmetric phase to a broken phase.

We show that simple grand unified theories, such as O(10), allow the mass scale at which parity conservation is presumably restored to be as low as 100-200 GeV.

A new resonance has been observed at very forward angles in the inelastic scattering of 200-MeV protons on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{94}{}_{}{}^{}\mathrm{Zr}$ at an excitation energy around 8.8 MeV in each target. The excitation energy, angular distribution, and strength of this state suggest that it corresponds to the previously unseen giant $M1\mathrm{}$ transition in the zirconium isotopes.

The collision-induced exothermic fine-structure transition $\mathrm{Ne}\left({}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}\right)-\mathrm{Ne}\left({}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}\right)$ has been observed in a crossed-effusive-beam experiment, by measuring the time of flight of metastable atoms scattered perpendicularly to the incident-beam plane. In this direction, the elastic scattering is kinematically discriminated. The identification of the transition is achieved by pumping ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ or ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ levels with a cw dye laser.

Zeros in dipole matrix elements for high-$Z$ elements are found to occur at significantly higher energies in our relativistic calculations than in nonrelativistic results. The energy separations of the zeros of the relativistic matrix elements are substantially magnified (a factor of ≳ 10) compared to the initial bound-state spin-orbit splitting.

Ultrastrong stationary double layers are generated in a magnetoplasma by simply applying potential differences between two plasma sources. The potential drop ${\varphi }_D$ of the double layer is increased up to $\frac{e{\varphi }_D}{T_e}\simeq 2\times {10}^3$ ($T_e$ is the electron temperature in eV) with no difficulties caused by gas discharge. There are always large spiky fluctuations on the low-potential tail of the double layers.

Observations of a form of three-dimensional turbulence, which occurs in beam-plasma interactions, are described. Large amplitude, beam driven instabilities in both the oblique electron plasma and electron-cyclotron modes are shown to collapse into thin, magnetic field aligned filaments, and to exhibit a variety of modulation time scales characteristic of both electron and ion modes in the system. On the largest time scales, associated density depletions are observed.

The ideal magnetohydrodynamic equilibrium and stability of a field-reversed theta pinch is investigated. Elongated, scalar pressure equilibria with no toroidal field are generated by a two-dimensional equilibrium code. Their stability is investigated in three-dimensional, nonlinear magnetohydrodynamic simulations. Experimental equilibria and stability properties are reproduced.

We report resonant inelastic light scattering by photoexcited electrons in GaAs-(AlGa)As multiple quantum-well heterostructures and find that a variable-density two-dimensional electron-hole plasma is created in a controlled manner. The energy levels and collective electron-electron and electron-phonon interactions were studied for carrier densities as high as ∼3×${10}^{12}$ ${\mathrm{cm}}^{-2\mathrm{}}$. Charge neutrality is preserved in each quantum well. Complex collective interactions occur among modes involving transitions between quantum-well states.