In transition arrays of complex atomic spectra, some well-defined subsets of lines bear the signatures, called scars, of their vanishing in one or several pure couplings. This is shown numerically, by means of line-by-line calculations, in the cases of the ${\mathit{d}}^{4\mathrm{-}}$${\mathit{d}}^3$p and ${\mathit{d}}^{8\mathrm{-}}$${\mathit{d}}^7$p transition arrays. It is also proved in a general way, using statistical distributions and the von Neumann–Wigner theorem.

The measurement of long (∼10 μs–100 ms) ionic autodetachment lifetimes utilizing a heavy-ion storage ring is demonstrated with 10–125 keV beams of ${\mathrm{Be}}^{\mathrm{-}}$. The lifetime of the metastable ${\mathrm{Be}}^{\mathrm{-}}$(2s2${\mathit{p}}^2$ ${}_{}{}^4{}_{}{}^{}$${\mathit{P}}_{3/2}$) state was found to be 45±5 μs, which represents an order-of-magnitude improvement in experimental accuracy over an earlier direct-beam-line experiment. This new result is a factor of 3 shorter than the recent theoretical value of 129 μs. New perspectives for storage-ring-based measurements of a variety of metastable lifetimes, both autoionizing and radiative, are briefly discussed.

The optical absorption spectra of small, isolated niobium clusters from seven to twenty atoms have been measured from 334 to 614 nm via photodepletion of niobium cluster-argon van der Waals complexes, ${\mathrm{Nb}}_{\mathit{n}}$${\mathrm{Ar}}_{\mathit{m}}$, in a moleculear beam. The absorption cross sections of all clusters in this size range increase with decreasing wavelength, as predicted by classical electrodynamic theory applied to small niobium spheres, however, the magnitudes of the cross sections are several times larger than predicted.

A theoretical model of the anomalous transport in torsatron-heliotron plasmas is developed, based on the current-diffusive interchange instability which is destabilized due to the averaged magnetic hill near the edge. An analytic formula of the transport coefficient is derived. This model explains the large edge transport, the power degradation and energy confinement scaling law, and the enhanced heat-pulse thermal conduction.

In response to a recent report [D. A. Bryant, R. Bingham, and U. de Angelis, Phys. Rev. Lett. 68, 37 (1991)] that makes the claim that electrostatic fields are weak in the auroral zone and that electrostatic fields cannot accelerate particles, it is pointed out that the evidence for electrostatic fields in the auroral zone is overwhelming and that these electrostatic fields often are accelerating electrons to produce aurora. The literature cited in the article above as evidence against double layers (strong electric fields) is reexamined and is found not to be evidence against double layers.

This Letter reports on numerical simulations showing exact, flat soliton solutions to a physical equation (that of Zakharov and Kuznetsov) breaking up into spherical solitons. Depending on the size of the box in which calculations are performed, the breakup can be either direct or via an intermediate, cylindrical soliton stage.

We have measured extremely large anisotropic thermal vibrations of gallium adatoms on a Si(111) surface using x-ray standing waves. At 830 K the rms amplitude normal to the surface is 0.47±0.02 Å while the parallel amplitude is 0.30±0.02 Å. The temperature dependence of these amplitudes deviates significantly from that expected from Debye theory and suggests a significant thermal softening of the surface bonding at elevated temperatures.

Evidence is provided for a new low-temperature superstructure in pure ${\mathrm{C}}_{60}$; its structure can be described as face-centered cubic with a lattice parameter 2${\mathit{a}}_0$. The superstructure is most probably the result of rotations alternatingly over +${\mathit{\phi }}_1$ and -${\mathit{\phi }}_2$ about one of the 〈111〉 axes of neighboring molecules along the cube directions. The experimental evidence is based on low-temperature electron diffraction.

The relative stability of various high-pressure phases of CsI is studied from first principles and analyzed using the Landau theory of phase transitions. We demonstrate that the cubic-to-orthorhombic transition recently observed to occur slightly below 20 GPa is driven by the softening of an acoustic phonon at the M point of the Brillouin zone. The coupling between this mode and anisotropic strain makes the transition slightly first order (with a volume variation of the order of 0.1%), and stabilizes the experimentally observed orthorhombic phase with respect to other competing symmetry-allowed structures.

Using a new quasiparticle detector and source consisting of a blackbody radiator, we have made the first measurements of the divergence of a beam of quasiparticles produced by a vibrating-wire resonator moving at supercritical velocities in superfluid ${}_{}{}^3{}_{}{}^{}\mathit{B}$ at the zero-temperature limit. At velocities just above the critical velocity of Δ/3${\mathit{p}}_{\mathit{F}}$ we see a very narrow beam directed along the direction of motion of the wire. As the maximum wire velocity increases the beam spreads to saturate at a half-angle divergence of approximately 55° at a maximum velocity of order Δ/${\mathit{p}}_{\mathit{F}}$.

We present a new method for performing finite-temperature ab initio total-energy calculations at long length scales, which we demonstrate with a dynamics calculation of 50 Å-long phonon modes in silicon. The method involves both a prescription for the analytic continuation of tradional fermionic energy functionals into the space of nonorthonormal single-particle orbitals (speeding convergence to the minimum) and insights into the common computational physics problem of solving by iterative refinement for the state of a complex system as a function of a continuous external parameter.

The radiative frequency shift of an exciton in a thin semiconductor film, like its radiative level width, is shown to be superradiatively enhanced. Unlike the latter, however, a finite frequency shift can only be obtained after proper renormalization for the correlated system. The shift is found to be inversely proportional to the square of the factor ${\mathit{k}}_0$d and proportional to the film thickness T, ${\mathit{k}}_0$=${\mathit{E}}_{\mathbf{q}\mathit{n}}$/ħc, ${\mathit{E}}_{\mathbf{q}\mathit{n}}$ being the exciton energy gap and d the lattice constant of the semiconductor. Therefore, the coherent frequency shift can be observed experimentally if one varies the thickness, or the exciton energy gap ${\mathit{E}}_{\mathbf{q}\mathit{n}}$ by imposing high pressure.

We study the consequences of the previously overlooked fact that in most quasi-one-dimensional materials with a Peierls-Fröhlich ground state the lattice zero-point motion is comparable to the lattice distortion. The density of states deviates significantly from that of a rigid lattice, containing a tail of strongly localized states below the gap. Moreover, thermal lattice motion causes the tail to increase significantly with temperature. This is consistent with the subgap optical absorption seen in these materials.

The traditional rules of effective-mass theory, that a substitutional dopant is a donor (acceptor) if it lies to the right (left) in the periodic table of the atom it replaces, are shown to be broken often in type-II-misaligned superlattices such as InAs/GaSb. Impurities commonly undergo deep-shallow transitions and transitions to ‘‘false valence,’’ and group-IV substitutional dopants can lose their amphoterism as remote layer thicknesses are varied.

We present a calculation of the inverse participation ratio in finite quasi-one-dimensional samples in the whole range of the scaling parameter within the framework of a one-dimensional nonlinear supermatrix σ model. The results are valid for both thick wires and random band matrices with large bandwidth and so are relevant for quantum chaos problems. The derived form of the scaling law exactly coincides with the empirical expression deduced earlier from results of computer simulations.

The power spectra of the 1/f noise in n-type-doped hydrogenated amorphous silicon (a-Si:H) are themselves time dependent. The noise power changes both in magnitude and as a function of frequency, reflecting a modulation of the properties of the fluctuators responsible for the current noise. Slow variations of the noise are strongly correlated over a broad range of frequencies. Spectral analysis of these noise power fluctuations, termed second spectra, also shows an approximate 1/f spectral slope, that is, the 1/f noise has 1/f noise. These results indicate that highly cooperative interactions exist between the fluctuators.

Spin-resolved inverse photoemission measurements of the n=1 image-potential-induced surface state on Ni(111) reveal a magnetic exchange splitting of 18±3 meV. The size of the splitting is in accord with calculations within the one-step model of inverse photoemission assuming the barrier potential as spin independent, but taking into account the different energy positions of the spin-up and spin-down band-gap boundaries. It is shown that spin resolution in experiments enables detection of splittings considerably smaller than the linewidths of the spectral features.

Linear elasticity theory of the vortex lattice in anisotropic and layered superconductors has a much wider range of applicability than in isotropic superconductors. This finding is used to calculate the energy barrier for thermally activated depinning of vortices from columnar pins along the c axis. The activation energy of these most effective line pins is strongly reduced by anisotropy. For very large anisotropy as in ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$, the length of the depinning vortex segment formally becomes shorter than the layer spacing; this means that the pancake vortices in the CuO layers depin individually.

The reflectivity and its temperature dependence in the neighborhood of the charge-transfer band is reported for carrier-free ${\mathrm{La}}_2$${\mathrm{CuO}}_4$. There is a sharp peak in the imaginary part of the dielectric function for light polarized parallel to the ${\mathrm{CuO}}_2$ layers. It is shown that the line shape as well as its temperature dependence is consistent with short-range electron-hole interaction in the final state of the charge-transfer excitation broadened by moderate coupling to optical phonons.

We consider a system of dilute magnetic impurities placed in a disordered metal, and examine the modifications of the Kondo temperature ${\mathit{T}}_{\mathit{k}}$ due to the presence of disorder. Our calculations, based on a slave-boson approach, show that the probability distribution P(${\mathit{T}}_{\mathit{K}}$) for Kondo temperatures can be related to the local-density-of-states fluctuations induced by localization effects. The resulting P(${\mathit{T}}_{\mathit{K}}$) is shown to be sufficiently singular to induce diverging magnetic susceptibility χ as T→0, a non-Fermi-liquid behavior.