The radiative corrections of heavy degenerate and nondegenerate electroweak multiplets do not decouple from low-energy experiments. Their effects can be parametrized in a general renormalization-scheme-independent way. For isospin-breaking ${\mathit{h}}_{\mathit{V}}$ and chiral-breaking ${\mathit{h}}_{\mathit{A}\mathit{Z}}$ and ${\mathit{h}}_{\mathit{A}\mathit{W}}$, derived from the Z and W self-energies, a global analysis of existing neutral-current and Z and W data yields -1.2<${\mathit{h}}_{\mathit{V}}$<0.9, -3.5<${\mathit{h}}_{\mathit{A}\mathit{Z}}$<1.0, -4.4<${\mathit{h}}_{\mathit{A}\mathit{W}}$<2.4 (90% C.L.). The expectations for future experiments are described, and the implications for the top-quark and Higgs-boson masses, new generations, supersymmetry, and technicolor are discussed.

We study the fluctuation properties of the spectrum and the electromagnetic E2 transitions of low-lying collective states in even-even nuclei. Using the framework of the interacting-boson model we discuss the transition between rotational and γ-unstable nuclei. Near those two limits the system exhibits regular behavior but in the transition region it shows chaotic behavior, where the fluctuations are characterized by the Gaussian orthogonal ensemble. Analysis of the classical mean-field dynamics of the five nuclear quadrupole shape degrees of freedom confirms the quantal results.

Geiger-Nuttall plots of the accurate modern data on partial half-lives for α decay yield very striking linear correlations. The plots for isotopic sequences which cross the neutron magic number N=126 show clearly the presence of different linear relations for N<126 and N>126. We indicate that this observation and all other data on ground-state to ground-state α decays for even-even nuclei with 76≤Z≤100 may be accounted for very well by a simple model with fixed parameters. An important ingredient in the model is the proposal that preformed α particles in the parent nuclei move in orbits with large values of a global quantum number.

The M1 excitation of ${\mathit{K}}^{\mathrm{\pi }}$=$1^{+}$ states in ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ through inelastic electron scattering is studied within a quasiparticle random-phase-approximation approach with quadrupole-quadrupole, spin-spin, and rotational-vibrational interactions. The calculated distorted-wave Born approximation (e,e’) form factors and the low-energy spectrum of $1^{+}$ states are in good agreement with the experimental data. The strongest experimentally observed $1^{+}$ states can be interpreted as isovector rotational vibrations, in which several quasiparticle pairs perform a scissors type of vibrational motion.

The linear polarization of Lyman-α radiation emitted when hydrogen atoms in the metastable 2${\mathit{s}}_{1/2}$ state traverse an external electric field is studied as a function of the effective rise time of the field for field strengths extending from very small values up to 6 keV/cm. With decreasing rise time, the measured polarization exhibits a transition from adiabatic to sudden behavior. The transition region is centered at a rise time which is approximately equal to the characteristic time associated with the 2${\mathit{s}}_{1/2\mathrm{-}}$2${\mathit{p}}_{1/2}$ Lamb splitting in the unperturbed hydrogen system. The experimental data are well described by the results of a time-dependent theory.

Solutions are reported for the problem of the motion of a two-dimensional interface between a viscous and a nonviscous fluid. The solution has the interface moving uniformly while the viscous fluid has a nontrivial potential flow. In an alternative interpretation, there are gravitational forces in the plane which allow the interface to be at rest while the fluid is in motion.

Particle-in-cell simulations of a high-power X-band dielectric Cherenkov maser experiment indicate strong particle bunching for drive currents greater than a few kA. Good agreement between the calculations and experimental measurements have been obtained. Depending on the parameters and configuration of the device, the simulations demonstrate power levels of up to 900 MW with rf conversion efficiencies of 37%. One-third of the total beam power can be contained in well-defined bunches which may be used to drive compact high-gradient linear acclerators.

A nonlinear simulation of the Cherenkov maser amplifier is presented for a configuration in which an electron beam propagates through a dielectric-lined cylindrical waveguide. The parameters used correspond to an experiment at General Dynamics which measured a total efficiency of 11.5% at 8.6 GHz. The simulation is in agreement with this but indicates that the system was too short to reach saturation and that an efficiency of 30% would have been possible for a longer system, and the performance is not significantly degraded by thermal spreads up to 20%.

Growth rates of the Rayleigh-Taylor instability were measured in targets with imposed sinusoidal modulations irradiated by optically smoothed 0.53-μm laser beams. A hybrid optical smoothing technique utilizing induced-spatial-incoherence and random-phase-plate technology was used for the first time. The wave-number dependence and the nonlinear behavior of Rayleigh-Taylor growth were investigated by using targets with a range of modulation periodicities and depths. The results are compared to 2D hydrodynamic-code simulations.

In a large laboratory plasma [1 m diam×2 m, ${\mathit{n}}_{\mathit{e}}$≤${10}^{12}$ ${\mathrm{cm}}^{\mathrm{-}3}$, ${\mathrm{\beta }}_0$≃15 G, ${\mathrm{\beta }}_{\mathit{e}}$=${\mathit{nkT}}_{\mathit{e}}$/(${\mathrm{\beta }}_0^2$/2${\mathrm{\mu }}_0$)≃0.5], strong density fluctuations (δn/n≃50%) near the lower hybrid frequency (${\mathrm{\omega }}_{\mathit{c}\mathit{e}}$${\mathrm{\omega }}_{\mathit{c}\mathit{i}}$${)}^{1/2}$ are identified as cross-field sound waves (${\mathit{k}}_{\mathrm{\perp }}$≫${\mathit{k}}_{\mathrm{\parallel }}$, ω/${\mathit{k}}_{\mathrm{\perp }}$≃${\mathit{c}}_{\mathit{s}}$) driven unstable by the electron diamagnetic drift ${\mathbf{v}}_{\mathit{d}}$=∇p×B/ne${\mathrm{\beta }}^2$, ${\mathit{v}}_{\mathit{d}}$>${\mathit{c}}_{\mathit{s}}$. Wave steepening and refraction saturate the instability. Wave-enhanced transport but insignificant particle acceleration are observed.

We report the first measurements of the superfluid density of thin ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ films for a broad range of thicknesses. In contrast to previous experiments, we find good agreement with the predictions of the general theory for the suppression of the superfluid transition temperature ${\mathit{T}}_{\mathit{c}}$. In addition, we find evidence for a new phase of the superfluid in films thinner than 2750 Å.

In the thin-cell electrochemical deposition of metals the interfacial velocity is shown, in the regime dominated by migration transport, to match the drift velocity of the counterion. The interfacial velocity is predicted to be independent of concentration to leading order and the deposit density is related to that of the electrolyte by the transport number of the counterion. Hecker-like pattern transitions occur when an acid front migrating in from the anode meets the deposit. The deposit radius at the transition is predicted to depend only on the ratio of ion mobilities.

The microscopic free energy is derived for dilute, interacting, tunneling elastic quadrupoles (TQ’s) randomly distributed in a nonpolar medium. For low TQ concentrations I obtain low-energy excitations very similar to those observed in glasses. The microscopic derivations give glasslike properties in the density of states, in the specific heat, in the thermal conductivity, in the sound absorption and propagation, and in the complex dielectric constant.

The interaction potential between the Pt(111) surface and Xe atoms adsorbed upon it was calculated using the cluster method with the Kohn-Sham scheme. For a single Xe atom, an energetically most favorable on-top adsorption site, 3.0 Å above a Pt atom, was found, with an activation energy for surface diffusion of 22 MeV and a perpendicular vibration energy of 8.5 meV. This vibration energy is reduced drastically by clustering of the adsorbed Xe atoms.

Submonolayers of Pb adsorbed on the Cu(110) surface form a series of uniaxial commensurate phases. We report the results of synchrotron x-ray scattering studies of the global phase behavior of this chemisorption system. We observe a floating-incommensurate to soliton-glass phase transition due to domain-wall pinning. The nature of this transition and other novel features revealed in this study are discussed in the context of current theories for strong adlayer systems.

Using a single crystal of ${\mathrm{AuCu}}_3$(001) as a test case, it is shown that x-ray-excited core-level photoelectron-diffraction patterns of an ordered alloy can be employed to decompose the total alloy density of states of the valence band into the partial densities of states of the constituents. The results of this new method are in good agreement with earlier experiments and recent band-structure calculations. The ratios of core-level to valence-band cross sections of each constituent of the alloy are also determined and compared to those of the pure elements. Within experimental error no changes of these cross-section ratios upon alloying are observed.

The resonant optical nonlinearities of GaAs/AlGaAs quantum wells are measured with femtosecond time resolution, as the quasi-two-dimensional states are further confined into quasizero dimensions by a perpendicular magnetic field. We apply fields up to 12 T to demonstrate that exciton-exciton Coulomb interactions are strongly modified by quasi-zero dimensional confinement, in agreement with many-body theory. These measurements demonstrate for the first time the remarkable result that at high magnetic fields an ensemble of 1s, electron-hole pairs behaves like a gas of noninteracting particles.

The conductance of linear arrays of two and three normal-metal small tunnel junctions is studied for bias voltages V below the Coloumb-blockade threshold. At low temperature, we find evidence for macroscopic quantum tunneling of the electric charge (q-MQT) through the Coulomb energy barrier. For double junctions the tunneling rate scales as ${\mathit{V}}^3$, and approximately as the product of the junction conductances, as predicted by the theory of inelastic q-MQT.

Electrons thermoemitted from cesiated surfaces of Ni(111) and cesiated polycrystalline Fe at temperatures between 400 and 450 K are unpolarized.