We demonstrate holographic reconstruction using low-energy electron-diffraction (LEED) and low-energy positron-diffraction (LEPD) intensity spectra. Calculated LEED and LEPD intensity spectra from a multiple-scattering method are inverted to produce high-fidelity images of near-neighbor atoms whose positions are measured from an adatom. We show that low-energy positron diffraction is better suited for holographic reconstruction because positron scattering in solids is weaker than that of electrons.

The magnetic signals emitted by a moving A-B interface are calculated using the spin hydrodynamic theory, including both the Leggett-Takagi relaxation and spin diffusion. The B-phase texture is appropriately simplified. Most experimental observations are well accounted for.

We present a theory of the magnetic properties of the A-B phase boundary propagating in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ under conditions of low temperature and therefore with slow magnetic relaxation. Owing to the difference in susceptibility between the phases, a nonequilibrium magnetization appears behind the moving A-B boundary. This magnetization is transported in the form of step solitons into the bulk A and B phases by a new spin supercurrent mode, related to the longitudinal NMR, which explains the experimentally observed magnetic precursor traveling ahead of that boundary.

Brillouin scattering spectra of the molecular glass former salol were combined with ultrasonic measurements to evaluate the nonergodicity parameter of mode coupling theory ${\mathit{f}}_0$(T). It was found to exhibit a weak cusp at a temperature ${\mathit{T}}_{\mathit{c}}^{\mathit{B}}$=275±10 K in reasonable agreement with the mode-coupling crossover temperature ${\mathit{T}}_{\mathit{c}}$=256±5 K found recently by other methods. This result is in marked contrast to the recent publication of Elmroth, Borjesson, and Torell [Phys. Rev. Lett. 68, 79 (1992)].

The zero-temperature optical properties of the t-J Hamiltonian are computed using the formalism of anyon superconductivity. Quantitative agreement is found with exact diagonalization studies.

We present experimental evidence that ferromagnetic order at room temperature in ultrathin epitaxial Co(001) layers on Cu(001) substrates is stabilized by in-plane magnetic anisotropies. All relevant anisotropy contributions have been determined as a function of Co layer thickness with and without an additional Cu overlayer.

Interlayer coupling in metallic multilayer is generally thought to be akin to the RKKY coupling of magnetic moments through conduction electrons. By analyzing recent experimental data on the spin polarization of chromium on iron substrates we confirm that the RKKY coupling cannot by itself explain the interlayer coupling in Fe/Cr multilayers. An additional coupling is warranted by the data, and we explain its origin.

We report the first direct measurement of the hot carrier cooling rate in a-Si:H. The femtosecond pump and probe technique with both 2 and 4 eV pulses was used to generate and probe directly hot carriers with considerable excess energy in the extended states of this material. The unexpectedly large average energy dissipation rate of 2 eV/psec obtained from our experiments suggests that disorder-enhanced carrier-phonon interactions may play an important role in the cooling process.

A pairwise particle-exchange model on a linear lattice is solved exactly by a new rate-equation method. Lattice sites are occupied by particles A and B which can exchange irreversibly provided the local energy is reduced. Thus, the model corresponds to a zero-temperature Kawasaki-type phase separation process. As a result of local order parameter conservation, the dynamics reaches a frozen state at large times, the structure of which depends on the initial conditions.

Coupled Hénon maps are introduced to model in a more appropriate way chaos in extended systems. An effective technique allows the extraction of spatiotemporal periodic orbits, which are then used to approximate the invariant measure. A further implementation of the ζ-function formalism reveals the extensive character of entropies and dimensions, and allows the computation of the associated multifractal spectra. Finally, the analysis of short chains indicates the existence of distinct phases in the invariant measure, characterized by a different number of positive Lyapunov exponents.

We report on the first measurement of the absolute phonon energy and the amount of ionization produced by the recoil of nuclei and electrons in a 60 g germanium cyrstal at a temperature of ≊25 mK. We find good agreement between our results and previous measurements of ionization yield from nuclear recoils in germanium. Our device achieves 10:1 discrimination between neutrons and photons in the few keV energy range, demonstrating the feasibility of this technique for large reductions of background in searches for direct interactions of weakly interacting massive particle dark matter.

Calculations with anomalous trilinear gauge boson vertices have been criticized as overestimates due to a failure to incorporate gauge invariance. We show here that the criticized calculations are gauge invariant, although this symmetry is realized nonlinearly. We instead trace the overestimates to an incorrect treatment of cutoffs in loop diagrams.

We show that higher-order vacuum polarization would contribute a measurable net charge to atoms, if the charges of electrons and positrons do not balance precisely. We obtain the limit ‖${\mathit{Q}}_{\mathit{e}}$+${\mathit{Q}}_{\mathit{e}\mathrm{¯}}$‖<${10}^{\mathrm{-}18}$e for the sum of the charges of electron and positron. This also constitutes a new bound on certain violations of PCT invariance.

We show that a lattice model for induced lattice QCD which was recently proposed by Kazakov and Migdal has a ${\mathrm{Z}}_{\mathit{N}}$ gauge symmetry which, in the strong coupling phase, results in a local confinement where only color singlets are allowed to propagate along links and all Wilson loops for nonsinglets average to zero. We argue that if this model is to give QCD in its continuum limit, it must have a phase transition. We give arguments to support the presence of such a phase transition.

We have analyzed events with jets and large missing transverse energy produced in p¯p colisions at √s =1.8 TeV. The observed event rate is consistent with standard model predictions. In a version of the supersymmetry (SUSY) model with a light photino (${\mathit{m}}_{\gamma }$̃<15 GeV/${\mathit{c}}^2$) and no cascade decays, we exclude at the 90% confidence level the existence of squarks and gluinos with masses less than 126 and 141 GeV/${\mathit{c}}^2$, respectively. The mass limits are lower with other choices of the SUSY parameters. An example is presented.

We derive a consistent set of light quark mass ratios which are compatible with the available constraints of chiral symmetry treated to next-to-leading order. Also required as input is resonance saturation of a set of low-energy amplitudes, in particular for the pion and kaon electromagnetic mass difference. The results (${\mathit{m}}_{\mathit{d}}$+${\mathit{m}}_{\mathit{u}}$)/${\mathit{m}}_{\mathit{s}}$=1/15.5, (${\mathit{m}}_{\mathit{d}}$-${\mathit{m}}_{\mathit{u}}$)/${\mathit{m}}_{\mathit{s}}$=1/29 are modestly different from previous values, and resolve the long-standing puzzle of the η→3π decay rate.

Identical rotational bands (i.e., those with surprisingly similar moments of inertia) have been proposed through several analyses of known bands in normally deformed nuclei. In this paper, we analyze bands in odd-proton nuclei (A=150–190) with criteria more stringent than those of previous approaches. The identical bands are found to be associated with up-sloping particle states, suggesting that the cause may be a cancellation between pairing and deformation decreases.

Coherent trapping of atomic population in sodium induced by two-frequency laser light has been studied by using a charge exchange reaction for probing the upper level population. When the two-photon resonance condition occurs, the signal due to electron capture from excited ${\mathrm{Na}}^{\mathrm{*}}$(3p) atoms by ${\mathrm{He}}^{2+}$ projectile ions exhibits the characteristic ‘‘black resonance’’ dip, indicating (by nonoptical means) that the fraction of Na atoms in the excited state actually drops to zero.

First above-threshold-ionization (ATI) spectra on a cesium atoms obtained with laser pulses as short as 70 fs are presented. Up to 7 ATI peaks exhibiting new substructure related to the extremely large Rabi coupling between the ground and first excited states have been detected. The angular and intensity dependence of the ATI signal has been studied. It is shown that the ATI peaks shift to higher electron energies with rising laser intensity. The obtained results are compared with a perturbative as well as a nonperturbative theory which predicts the structure.

Negative chlorine ions, held in a Penning ion trap, are irradiated by intense (up to 2×${10}^{16}$ W/${\mathrm{m}}^2$) Raman-shifted light of a Nd:YAlG laser with a wavelength of 1098 nm and a pulse duration of 30 ps. Electron-energy spectra are obtained showing up to 11-photon absorption. In the case of circularly polarized light suppression of the low-energy channels is observed. A saturation intensity of (8.5±2.5)×${10}^{15}$ W/${\mathrm{m}}^2$ is found for multiphoton detachment of ${\mathrm{Cl}}^{\mathrm{-}}$ by 1908-nm light. This result is counterintuitive because it is lower than the saturation intensity for multiphoton detachment at 1064 nm.