It is shown that the quasielastic peak in electron scattering from metallic surfaces has the form P(ω)∼‖ω${\mathrm{\Vert }}^{\mathrm{b}\mathrm{-}1}$ with b∼ρT where ρ is the metal resistivity and T is the temperature.

Small solid-Ar bubbles, formed by the implantation of 50-keV ${\mathrm{Ar}}^{+}$ ions into Al, are observed to melt at 730 K, compared with an equilibrium bulk melting temperature of 250 K. A model based on the suppression of Ar thermal vibrations at the Al interface is used to account for the superheating of 480 K. Measurements on the temperature dependence of diffracted electron intensities from these bubbles yield Debye-Waller factors consistent with an effective Debye temperature of about 140 K, compared with a bulk value of 110 K.

We have created extremely small and independent Bose systems by confining ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ in bubbles of radius of less than 110 Å in Cu foils. The size distribution and density of the bubbles were adjusted by annealing the samples and were determined by transmission electron microscopy. At low temperatures the confined helium becomes first solid, then liquid, and eventually superfluid as the mean bubble size is increased by annealing. The modification of superfluidity in this new confining geometry by size effects has been investigated by low-temperature calorimetry.

The first neutron-diffraction study of the helical phase of Gd-Y alloys in the vicinity of 30 at.% Y is presented. For each alloy composition the turn angle of the helix is seen to go smoothly to zero at the phase boundary with the low-temperature canted-ferromagnetic phase. The initial (onset) turn angle decreases rapidly with increasing Gd concentration, tending to zero at ∼29.7 at.% Y. Combining the neutron data with magnetization, resistivity, and ultrasonic data allows us to construct a definitive magnetic phase diagram for the Gd-Y system. Two multicritical points are observed but neither complies fully with all the conditions necessary for a Lifshitz point.

It is shown that the magnetic-field-induced superconducting state recently observed in the system ${\mathrm{Eu}}_{\mathrm{x}}$${\mathrm{Sn}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Mo}}_6$${\mathrm{S}}_8$ has new and unexpected magnetic properties. In particular, for a certain applied field, the external field will penetrate completely and uniformly into the superconductor. Below this field the superconductor contains antivortices and the magnetic field is enhanced in the superconducting regions. A first observation of the paramagnetic nature of this state is presented.

Direct experimental proof of impurity Auger recombination in silicon is given by measurement of the weak luminescence from highly excited carriers which are produced in the Auger process. Gold, iron, and chromium used as deep impurities have been identified spectro- scopically by the energetic shift from the 2${\mathrm{E}}_{\mathrm{g}}$ emission corresponding to their levels in the gap.

The initial adsorption of oxygen on Si(111) surfaces proceeds via a molecular intermediate which is precursor to the stable dissociated adsorption state. This metastable precursor can only be observed under certain conditions; its conversion to the stable state depends on temperature, probe, surface structure, impurities, and oxygen coverage. The precursor is likely to be a peroxy-bridge configuration whereas the stable dissociated oxygen species forms short-bridge bonds between adjacent Si atoms.

${\mathrm{Cs}}_3$${\mathrm{Cr}}_2$${\mathrm{I}}_9$ represents a novel class of antiferromagnetic dimerized singlet-ground-state systems. Neutron scattering shows a transition to magnetic order below 7 K. The soft mode was identified as an intratriplet mode rather than a singlet-triplet exciton mode by relation of the magnetic order to the spin dynamics. A reduced magnetic moment of the ${\mathrm{Cr}}^{3+}$ ions is ordered ferromagnetically within the dimers even though the corresponding interaction is antiferromagnetic.

Aperiodic oscillations are observed in the magnetoresistance of narrow inversion layers in p-type Si. The dependence of the oscillations on Fermi energy indicates that they are not the result of a shift with magnetic field of the energies of electronic states but rather arise from a change in the phase of the wave functions.

It is shown that the Hamiltonian describing the acoustic many-polaron dynamics in one spatial dimension is identical, except for the cutoff procedure, to that of an exactly solvable field theory. Cutoff independent quantities, such as the spectrum of excitations and dynamical correlation functions, are computed. A critical coupling is found above which there is a condensation of polaron pairs and the system exhibits a polaronic superconductivity. Below the critical coupling, the spectrum contains only collective excitations of polarons and the system has a metallic behavior.

The spin-forbidden f-f multiplet excitations are observed for the first time as the strongest features in the electron-energy-loss spectra of Gd, Dy, and Sm metals at low primary-electron energies. The exchange nature of the excitation process is argued, in analogy with that of spin-flip Stoner excitations in d-band ferromagnets. A resonance enhancement observed for primary-electron energies near the 4d-4f core threshold is found to be consistent with the proposed mechanism.

The well-known Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between localized spins in metals is accompanied by conduction-electron scattering that induces transitions between different multiplets of the spins, in some circumstances strongly so.

Silver cluster ions (${\mathrm{Ag}}_1$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_3$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_4$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_5$${\mathrm{}}^{+}$, ${\mathrm{Ag}}_7$${\mathrm{}}^{+}$, and ${\mathrm{Ag}}_9$${\mathrm{}}^{+}$) generated in a sputtering arrangement were filtered in energy selected by size, and deposited onto specimens containing binder-free AgBr microcrystals prepared from a photographic emulsion. Development was observed after exposure to beams containing ${\mathrm{Ag}}_4$${\mathrm{}}^{+}$ or larger aggregates. No development occurred after exposure to beams of smaller cluster sizes. These experiments prove directly the existence of a ‘‘critical’’ size required for catalyzing development. This size may depend on the development conditions (e.g., the redox potential), as suggested by theories.

The evolution of a distribution function according to the linearized relativistic Boltzmann equation is shown to be causal for a wide class of scattering cross sections.

We discuss gauge models in which exchange of Goldstone bosons combined with the QCD anomaly can lead to spin-independent 1/R and T-nonconserving σ⋅r^/$R^2$ potential. In contrast with axion-exchange forces which lead to new short-range macroscopic forces (range ∼10 cm), these forces could be observable in Eötvös-Dicke–type experiments involving polarized and unpolarized materials.

By calculating Polyakov loop averages on a ${60}^2$×2 lattice, we determine the critical exponent of deconfinement for SU(2) gauge theory in 2+1 dimensions. Universality arguments predict it to be the same as the critical exponent β=(1/8) for the spontaneous magnetization in the two-dimensional Ising model. Our results are in good accord with this prediction.

Gross-structure resonances previously observed only in inclusive measurements have been studied in both single and mutual inelastic scattering involving the $0_2^{+}$ state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Analysis of the excitation functions in the single-excitation channel at the zeros of Legendre polynomials permits the dominant L values to be determined for most of the resonances. The measured spins disagree with the predictions of a recently published microscopic model of the inelastic-scattering process.

The interacting-boson-model Hamiltonian is written uniquely as a sum of an intrinsic part which defines bands and a collective part which shifts, splits, and mixes these bands.

The linear density response of inhomogeneous electronic systems is discussed from a density-functional point of view. We derive a local density approximation for the frequency-dependent exchange-correlation potential which is compared with the ‘‘adiabatic’’ expression used in former work.

Accurate ab initio molecular-orbital calculations are performed to obtain the ground-state geometries and electronic configurations of the silicon clusters ${\mathrm{Si}}_{\mathrm{n}}$ for n=2–7,10 and ${\mathrm{Si}}_{\mathrm{n}}^{+}$ for n=2–6. The effects of polarization functions and electron correlation are included in these calculations. All the optimized structures are considerably reconstructed from those derived from microcrystal geometries. Ionization potentials and binding energies are calculated and used to interpret the distribution and fragmentation of small silicon cluster ions observed recently.