We study the excitation spectra and the dynamical structure factor of quantum Hall states in a finite-size system through exact diagonalization. Comparison is made between the numerical results so obtained and the analytic results obtained from a modified random-phase approximation in the preceding companion paper. We find good agreement between the results at low energies.

The binding energies ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^0$) and ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^{\mathrm{-}}$) of neutral and negative donor (${\mathit{D}}^0$ and ${\mathit{D}}^{\mathrm{-}}$) centers in quantum dots (QD’s) with different dimensionality and potential shape have been obtained by a variational approach with a trial function, which consists of the exact solutions of ${\mathit{D}}^0$-like ground states in the dots, includes the electron-correlation effect, and approaches the Chandrasekhar-type trial function at zero barrier height. The dimensionality and potential-shape effects of QD’s on ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^0$) and ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^{\mathrm{-}}$) have been studied in detail. It has been found that the electron-correlation effect on ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^{\mathrm{-}}$) depends on the dimensionality and decreases with increasing confinement. The ratio σ of ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^{\mathrm{-}}$) to ${\mathit{E}}_{\mathit{B}}$(${\mathit{D}}^0$) approaches a constant value in the limit of strong confinement. It has been shown that the ratio σ and the electron-correlation effect are strongly dependent on the dimensionality of QD’s and weakly dependent on the potential shape. Using the value of the σ obtained, calculated results of different quantum-well structures can be checked and compared with others.

Electronic effects from two well-defined defects are identified and measured using scanning tunneling microscopy on graphite. An atomic vacancy on the topmost (0001) plane caused a lowering of apparent z height in a 30 Å×30 Å area by ∼1.5 Å. A plane rotation relative to the third surface layer caused a Moiré pattern, with an attenuation along the c axis about 2.6 per monolayer. A ‘‘supervacancy’’ was imaged due to competition between the above two effects. An explanation based on changes in density of states near the Fermi level is proposed.

Ground-state structures of singly charged copper-cluster anions have been calculated with simulated annealing using a simple total-energy scheme based on the effective-medium theory with a tight-binding description of the discrete one-electron spectrum. The results are compared to previous theoretical results for neutral clusters and to recent experimental photoelectron spectra. Agreement between theory and experiment is fair. The important quantity governing properties of the cluster ground-state structure such as energy fine structure, electronic level spectra, and geometry is the number of delocalized electrons rather than the number of atoms in the cluster.

To produce high-quality, low-scatter optical interference coatings, substrates with extremely smooth surfaces are required for deposition. For successful production surface roughness characterization of the substrates before coating is essential. Light-scattering measurement is a nondestructive and fast surface characterization technique that determines statistical surface properties such as the power-spectral-density function (PSD) and the rms roughness ${\mathrm{\delta }}_{\mathrm{rms}}$. Scatter measurement is an accepted tool to characterize opaque surfaces and optical interference coatings. Its application to characterize the surfaces of transparent substrates—commonly used for deposition—is difficult due to the low scatter intensities of high-quality substrates and the scattering contribution of the substrate’s back surface. In this paper the total scattering distribution of a transparent substrate is calculated, considering the scattering contributions of the front and the back surface. With the theoretical result obtained, PSD’s of the substrate interfaces can be calculated from angle-resolved-scattering measurement and rms roughness from the total integrated scattering measurement.

An observation of photoconductivity in a homonuclear semimetal (bismuth) is reported. The effect is observed when bismuth films of different thicknesses are irradiated with 1.064-μm laser pulses. The sign and the temporal evolution of the resistivity change induced in the films are studied. An anomalous resistivity change due to laser heating is observed in the thickest film. A theoretical interpretation that explains and fits the experimental behavior well is given. The results support the predictions of a previously reported model that required the pumping of carriers into a metastable band by the laser light. The sum of the mobilities and of the diffusion coefficients for electrons and holes in this band are also estimated.

Ab initio molecular-orbital calculations of the carbonyls of 3d transition metals are used to indicate the tilted metal-CO complex as the molecular state precursor of CO dissociation on 3d surfaces. The present resonating-valence-bond mechanism for CO dissociation suggests that the tilted state may be observed in all dissociative 3d surfaces, that is, from Sc to Fe. Calculations of scandium monocarbonyl are used to understand the effects of inclination on electronic configuration and calculations of ${\mathrm{Cr}}_2$CO cluster are used to study CO dissociation on the Cr(110) surface and to explain the substantial reduction of CO binding modes found for the tilted state.

Spin-polarized electron-energy-loss spectroscopy was applied to study electron-exchange processes in insulating NiO(100). Dipole-forbidden d-d excitations of the ${\mathrm{Ni}}^{2+}$ ion give rise to sharp gap structures in the energy-loss spectrum. Our measurements show strong spin-flip electron-exchange scattering in the excitations with 1.1- and 1.6-eV energy loss up to high primary electron energies of more than 100 eV. No spin-flip exchange scattering is found in the excitations leading to the loss structure around 2.8 eV.

The average multipole surface-plasmon energy for simple metals, as well as that of ordinary surface and bulk plasmons, is obtained using energy-weighted moments of the electronic response to sufficiently general external perturbations. A local approximation of exchange and correlation effects is used within a jellium model. Band-structure effects are incorporated through an effective electronic mass. Taking advantage of the transparency of the method, we analyze under what circumstances such modes might be observable. It is shown that due to an interplay between Coulomb and kinetic energies, the multipole modes become unobservable for increasing values of the transferred momentum (q) parallel to the surface. The value of q at which the multipole mode becomes unobservable is much smaller than the cutoff value for Landau damping. The effect of the electronic surface diffuseness is also analyzed. We compare our results with previous density-functional calculations and with recent experimental data for Na, K, and Cs.

The resonant electron transfer processes that occur when slowly moving atoms and (positive) ions interact with metal surfaces are theoretically analyzed with regard to scaling properties and universal behavior. Within the first-order adiabatic approximation, a simple model is employed that allows a systematic (formal and numerical) study of the dependence of transition matrix elements and transition rates upon the parameters characterizing the ion-metal system. Scaling parameters are introduced, through which scale transformations of the system parameters are defined. The ion-surface distance, in particular, is scaled by means of the ‘‘classical threshold distance,’’ below which, at given electronic energy, resonant electron transfer is classically allowed. When transformed to the scaled representation, transition matrix elements and rates are found to be expressible in terms of ‘‘reduced,’’ universal functions, which are independent of the parameters characterizing the strength of the electronic potentials in the ion-metal system. In the limit of large ionic principal quantum numbers, the behavior of transition matrix elements and rates is largely determined by three universal functions that depend on the scaled ion-surface distance only. Scaling laws connecting transition matrix elements and rates for different ionic principal quantum numbers are established. Resonance neutralization of highly charged ions and resonance ionization of Rydberg atoms are considered as specific cases. Quasiclassical aspects and possible applications of our results as well as extensions of our analysis are briefly discussed.

A method is presented for separating ‘‘bulk’’ and ‘‘surface’’ contributions to the strain derivative of the total energy of a two-dimensionally periodic, several-layer slab. The method, involving a layerwise decomposition of the sums and integrals required to calculate the derivative, makes it possible to compute a surface stress via a single, linear combination of atomic orbitals slab calculation. Application to Al(111) yields a predicted tensile surface stress of magnitude 0.090 eV/A${\mathrm{̊}}^2$.

In this paper we study the relationship between equilibrium and kinetics in Cu-Ag (111). We investigate the kinetics of segregation in a silver–dilute-copper sample and the dissolution kinetics of one Ag monolayer deposited on Cu(111). We compare results obtained using mean-field and Monte Carlo methods and relate them to the equilibrium isotherm by means of a local-equilibrium concept. We find good agreement with available experimental results on segregation kinetics and on dissolution kinetics when the Monte Carlo simulation is used.

A general formalism is developed to include thermal vibrations and local static disorder into tensor-LEED calculations. The given expression for the averaged t matrix is based on a cumulant expansion for the probability distribution of atomic displacements. The method is a generalization of the concept of temperature-dependent scattering phase shifts and allows an efficient description of both anisotropy and anharmonicity of thermal motions, which are important in particular for adsorbate atoms and substrate atoms in the topmost layers.

The interaction of ${\mathrm{Cl}}_2$ with GaAs(110) was studied with photoelectron spectroscopy at 300 K. The results show that ${\mathrm{Cl}}_2$ dissociates and prefers ${\mathrm{Ga}}^{1+}$ bonding at low coverage and chemically distinct states can be correlated with structural information obtained from scanning tunneling microscopy. This Cl-Ga state was characterized by a distinct surface bonding configuration as Ga atoms lost charge, As atoms gained charge, and the surface bonds became less ${\mathit{sp}}^3$-like. The result was a chemical shift for both Ga and As. Cl-Ga islands developed as the Cl coverage increased and subsequent adsorption of Cl within those islands enabled the formation of Cl-As bonds and an ${\mathrm{As}}^{1+}$ state.

We report on the systematic investigation of neutralization of low-energy ${\mathrm{D}}^{+}$ ions scattered from 17 ionic-compound surfaces with particular emphasis on the relation between the neutralization probability of ${\mathrm{D}}^{+}$ and the ionicity of the surface atomic bonds. The ${\mathrm{D}}^{+}$ ions tend to survive neutralization provided that the target atom is completely ionized, whereas almost complete neutralization results if the target has covalent or metallic orbital hybridization with the ligand. The ${\mathrm{D}}^{+}$ spectra from nitrates, sulfates, and carbonates of Na and K, as well as ${\mathrm{K}}_2$${\mathrm{SiO}}_3$, exhibit surface peaks of ${\mathrm{D}}^{+}$ surviving neutralization for both cations and oxygen, indicating large ionicity in the alkali-metal–oxygen bond. Rather exceptional is ${\mathrm{Na}}_2$${\mathrm{SiO}}_3$, for which a relatively small ionicity is concluded from the absence of surface peaks. For the alkaline-earth compounds, ionicity decreases in going to the light elements as evidenced by the decrease of the surface-peak intensity. The occurrence of charge-exchange relaxation between cations and anions of ${\mathrm{NiSO}}_4$ and ${\mathrm{CuSO}}_4$ results in large neutralization probability of ${\mathrm{D}}^{+}$, while the closed-shell structures of ${\mathrm{Ag}}^{+}$ (4${\mathit{d}}^{10}$) and ${\mathrm{Pb}}^{2+}$ (6${\mathit{s}}^2$) in ${\mathrm{AgNO}}_3$ and Pb(${\mathrm{NO}}_3$${)}_2$, respectively, suppress neutralization to some extent so that the appreciable surface peaks appear.

A problem in studying optical nonlinearities is the fact that the important analyzing tools—the dispersion relations for nonlinear susceptibilities—can be applied only in the nondegenerate case (excluding the cases of harmonic generation). We show that a maximum entropy procedure can be utilized in computing the phase of the complex degenerate nonlinear susceptibility [e.g., ${\mathrm{\chi }}^{\mathrm{}\left(3\right)\mathrm{}}$(ω,ω,-ω)] from its amplitude spectrum [‖${\mathrm{\chi }}^{\mathrm{}\left(3\right)\mathrm{}}$(ω)‖, ${\mathrm{\omega }}_1$≤ω≤${\mathrm{\omega }}_2$].

We have designed, fabricated, and tested a three-dimensional photonic-band-gap structure. The structure is built by an orderly stacking of dielectric rods. A network analyzer is used to measure the transmission and dispersion relations of electromagnetic waves along several crystal directions. The experimental results are in good agreement with the theoretical calculations. The structure is different from that previously suggested, as it is already used to improve the midgap frequency by almost two orders of magnitude, and it offers a viable geometry to extend the photonic band gap to optical regimes.

We show that the nonparabolicity and spin splitting enhance electron effective mass appreciably in a quantum wire. In bulk materials, these effects are usually small since electrons are near the conduction-band edges. In quantum wires, strong confinement puts the electrons far from the conduction-band edge, giving rise to large nonparabolicity effects. We derive a simple expression for the effective mass parallel to the transport direction in the quantum wire, taking into account the band nonparabolicity, anisotropy, and spin splitting. We apply our formalism to GaAs/${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As quantum wires and find that the parallel mass could be 50% more than the bulk value for a wire width of 50 Å.

We develop a microscopic theory for charge transfer through a single-electron transistor containing a superconducting grain. Both tunnel current and shot noise are shown to be sensitive to the parity of the electron number on the grain. In particular, tunneling may cross over from pair channels to two distinct single-particle channels at finite voltage. The two corresponding threshold voltages are sensitive to the circuit parameters. While it is difficult to identify them from the I-V curve, they can be determined from the normalized zero-frequency noise and the finite-frequency noise spectrum.

The longitudinal resistivity ${\mathrm{\rho }}_{\mathit{x}\mathit{x}}$ at the quantum Hall midplateau of a low-mobility two-dimensional electron gas in a GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterostructure has been studied for different sample widths and different sample currents. The critical current for breakdown of the quantum Hall effect was found to be proportional to the width of the samples. A subcritical rise of ${\mathrm{\rho }}_{\mathit{x}\mathit{x}}$ with current density was found to be exponential, a relation which to the best of our knowledge has not previously been reported. The power dissipation thus increases exponentially with current, leading to a critical current determined by a thermal runaway.