We invert high-energy (E≥400 eV) photoelectron and Auger-electron interference patterns to construct 3D images of surface and interface atoms. A new scheme is introduced to correct the phase shift of the image. Image reconstruction is demonstrated for Si(111) √3 × √3 -B, a system in which multiple-scattering effects are small and all source waves are equivalent. Using diffraction results from multiple-scattering slab calculations, we achieve a spatial resolution of 1.0–1.3 Å, thus qualifying the technique as a direct structural tool.

Quasiparticle calculations have been performed for the band gap of solid molecular hydrogen in the hcp structure. The calculations predict that the orientationally ordered phase undergoes metallization due to an indirect band overlap at the volume V=2.50 ${\mathrm{cm}}^3$/mol and the orientationally disordered phase at V=1.89 ${\mathrm{cm}}^3$/mol, which correspond to metallization pressures of 151 and 300 GPa, respectively. A quantitative relation between the degree of orientational order and the metallization volume is obtained.

A detailed analysis of the photoionization process of DX(Te) centers in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As (0.25<x<0.55) for different temperatures and light intensities revealed, for the first time, that the process goes through two steps. The only possible interpretation of the phenomenon is by means of a negative-U character of the defect; i.e., the center binds two electrons in the ground state, forming a ${\mathit{DX}}^{\mathrm{-}}$ energy state. An intermediate state for the process is a one-electron localized state of the defect.

The Schottky-barrier height (SBH) of an epitaxial ${\mathrm{NiSi}}_2$ layer grown on Si(100) is shown to depend critically on the morphology of the interface. Single-crystal, uniform, planar ${\mathrm{NiSi}}_2$Si(100) layers have a much lower (n-type) SBH than that of interfaces which are made up of inclined 〈111〉 facets. Interfaces with both planar 〈100〉 sections and inclined 〈111〉 sections exhibit electrical behavior expected of a spatially inhomogeneous SB. We suggest that interface atomic structure determines SBH formation.

We show that the differential contribution, at energy E, to the persistent currents of independent electrons in infinitely extended quantum systems is given by (2πi${)}^{\mathrm{-}1}$${\mathrm{\partial }}_{\mathrm{\phi }}$ [ln detS(E,φ)]dE, where S(E,φ) is the (on-shell) scatteirng matrix. We apply this result to the calculation of the persistent currents in two examples: a mesoscopic loop connected to one infinitely long lead, and a plane pierced by a flux line. In the last example spin plays a remarkable role.

It will be shown that the magnitude of persistent currents increases the more that fluctuations in the charge, i.e., in the electron density, are suppressed. This explains the peculiar role of the Coulomb interactions between electrons and ions which enforces local charge neutrality.

We present a microscopic calculation of the disorder-averaged persistent current for a mesoscopic ring with a fixed number of electrons. Using an idea by Imry, we show that the even Fourier components of the average current dominate and are related to the typical single-lvel current 〈${\mathit{I}}_{2\mathit{p}}$${\mathrm{〉}}_{\mathit{D}}$∝〈${\mathit{i}}_{\mathit{p}}^2$${\mathrm{〉}}_{\mathit{D}}$/${\mathit{I}}_0$, which can be calculated by a Green’s-function averaging technique. For the small, even harmonics p, the result simplifies to 〈${\mathit{I}}_{2\mathit{p}}$${\mathrm{〉}}_{\mathit{D}}$≊${\mathit{I}}_0$/2πM, where M is the number of transverse channels. Its relevance to multiring experiments is discussed.

Disorder-averaged thermodynamic quantities within the canonical ensemble are expressed in terms of fluctuations in the grand canonical ensemble, and are then evaluated for the diffusive regime. The particular example of persistent currents in Aharanov-Bohm geometries is addressed, and the harmonics of the disorder-averaged current (which is 1/2${\mathrm{\Phi }}_0$ periodic) are obtained. The orbital susceptibility of a mesoscopic system, disorder averaged over the canonical ensemble, may be large and positive, even for systems which, on a larger scale, should exhibit Landau diamagnetism.

Searches for possible day-night and semiannual variations of the ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ solar neutrino flux are reported based on 1040 days of Kamiokande-II data. Within statistical error, no such short-time variations were observed. The limit on the day-night difference sets a constraint on neutrino-oscillation parameters. A region defined by ${\sin }^2$2θ>0.02 and 2×${10}^{\mathrm{-}6}$≲Δ${\mathit{m}}^2$≲${10}^{\mathrm{-}5}$ ${\mathrm{eV}}^2$ is excluded at 90% C.L. without any assumption on the absolute value of the expected solar neutrino flux.

Numerical results on the static critical behavior of a collective-pinning model of charge-density waves are presented. Distinct critical behaviors are found for irreversible (typical) and reversible approaches to the threshold for sliding. From the size dependence of the threshold fields and polarizations, at least two distinct finite-size-scaling correlation-length exponents are identified. New analytic results on the general behavior of this model both above and below threshold are reported, including the uniqueness of the sliding state.

Nuclear magnetic resonance on oriented nuclei (NMR-ON) on Y as a dilute impurity in Fe was observed for the first time. As all attempts to observe NMR-ON resonances on YFe samples prepared by conventional techniques had failed, a new sample-preparation technique was applied. After the implantation of radioactive precursor isotopes and their in situ decay to Y, narrow NMR-ON resonances were observed. Our results indicate that all previous values for the hyperfine field of YFe in the literature do not represent the field at substitutional lattice sites.

A family of Hilbert spaces with a positive-definite inner product is constructed which interpolates analytically between the Fock spaces representing Fermi and Bose particles. It is shown that the physically unallowed subspaces in the two limiting cases correspond to the appearance of states of zero norm.

The effect of external white Gaussian noise on the invariant measure of a periodically driven damped nonlinear oscillator is studied by solving for the first time the full three-dimensional Fokker-Planck equation by numerical means. We critically discuss and interpret deterministic concepts and stochastic notions in the presence of noise and chaos.

We study the bound-state spectrum of many particles obeying fractional statistics (anyons) in a two-dimensional system in the presence of an external potential and a large magnetic field B. As a function of B, there occur periodic recurrences of quantized states at fixed energy. For fixed particle number, the period is determined by the fractional charge, while at fixed chemical potential, the fractional charge is masked by the fractional statistics. We discuss the relevance of these results to recent experiments in quantum Hall devices, and we propose a simple extension of these experiments which could measure the fractional statistics.

Two examples are given that substantially simplify the no-hidden-variables theorem of Kochen and Specker, greatly reducing the number of observables considered and requiring no intricate geometric argument. While one of the examples also obeys a more powerful version of Bell’s theorem, the other does not. The examples provide a new perspective on both of these fundamental theorems and on the relation between them.

We study the phenomenology of baryon-number violation induced by electroweak instantons and find that if the naive instanton amplitudes were valid for arbitrarily high energies, the event rate at the Superconducting Super Collider could be a few per hour. A typical event would consist of three ‘‘primary’’ antileptons and seven ‘‘primary’’ antiquark jets, accompanied by ∼85 electroweak gauge bosons, having a sharp threshold in the total subenergy at about 17 TeV. However, the instanton approximation is not valid at such high energy (above the sphaleron energy), so that new theoretical methods are needed.

There is some theoretical uncertainty in the predictions for CP-violating hadronic asymmetries in neutral-B decays to CP eigenstates due to the existence of penguin diagrams. Using isospin relations, we show that it is possible to remove this uncertainty for the decays ${\mathit{B}}_{\mathit{d}}^0$→ππ.

The evolution of the atomic state in the resonant Jaynes-Cummings model (a two-level atom interacting with a single mode of the quantized radiation field) with the field initially in a coherent state is considered. It is shown that the atom is to a good approximation in a pure state in the middle of what has been traditionally called the ‘‘collapse region.’’ This pure state exhibits no Rabi oscillations and is reached independently of the initial state of the atom. For most initial states a total or partial ‘‘collapse of the wave function’’ takes place early during the interaction, at the conventional collapse time, following which the state vector is recreated, over a longer time scale.

The interaction of transverse eigenmodes with a relativistic electron beam is analyzed in an overmoded cyclotron autoresonance maser amplifier, using a nonlinear self-consistent model and kinetic theory. It is shown that all of the coupled modes grow with the dominant unstable mode at the same growth rate, but suffer different launching losses. The phases of coupled modes are locked in the linear and nonlinear regimes. Simulations indicate that the rf power distribution among the interacting modes at saturation is insensitive to input power distribution but sensitive to detuning.

The photoelectron counts of spontaneous light from the wiggler in the Brookhaven electron storage ring obey the negative-binomial distribution, in accord with the predictions of a multielectron, multimode theory. The bending-magnet light emerging from the Pyrex exit port of the storage ring obeys the Neyman type-A distribution.