The description of the spin-glass phase in terms of a $T=0\mathrm{}$ fixed point is shown to imply a "chaotic" phase in which the relative orientations of spins with large separations $L\gtrsim L^{*}$ are sensitive to small changes $\delta T$ in the temperature or $\delta J$ in the bond strengths, where $L^{*}\propto \frac{1}{{\left(\delta T\right)}^{\frac{1}{\zeta }}}$ or $\frac{1}{{\left(\delta J\right)}^{\frac{1}{\zeta }}}$, respectively, $\zeta =\frac{d_s}{2-y}$, and $-y$ and $d_S$ are the thermal eigenvalue at the $T=0\mathrm{}$ fixed point and the "interfacial (fractal) dimension," respectively.

We consider the effects of $Z^0-Z^{\prime }$ mixing, where the $Z^{\prime }$ is an $E_6$ gauge boson, on processes which will be measured at $e^{+}{e}^{-}$ colliders. Using constraints from current data, we find that significant mixing may be allowed. This mixing leads to measurable changes in the $Z^0$ partial widths and $\sigma (e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-})$. In one case, we also find that a $Z^{\prime }$ lighter than the $Z^0$ is still allowed. We discuss possibilities for its detection.

The appearance of localized grain-boundary electronic states is shown to provide a reliable indication of intergranular fracture in polycrystalline materials. Representative densities of states are presented for some $L{1}_2$ intermetallic compounds by use of polyhedral models of grain-boundary structure. The role of certain segregated impurities as inhibitors of intergranular brittleness is briefly discussed and suggestions are made for direct experimental verification of our model.

It is shown by model calculations that the dispersion of the diagonal part of the dielectric constant near the plasma edge in a metallic crystal has a strong influence on the magneto-optical properties. The plasma edge leads to resonancelike peaks in the Kerr rotation and Kerr ellipticity spectra and to a strong enhancement of the magnitude of the Kerr effect. The sharp and very large peaks observed in the Kerr effect of several transition-metal and rare-earth compounds are not necessarily related to sharp magneto-optical transitions, but could be a result of the presence of the plasma edge at the same frequency.

The melting of thin silicon films with continuous laser radiation is characterized by the formation of several distinct and reproducible microscopic patterns of solid and molten regions with various degrees of long-range order. The pattern formation reflects the competition between the coherent energy deposition from the laser beam and the incoherent heat loss via diffusion. A phase, or stability, diagram of the structures has been constructed and order-disorder nonequilibrium "phase" transitions between these melt morphologies have been demonstrated by changes of the laser intensity and/or spot size.

We use infrared cyclotron-resonance measurements to study the dynamical conductivity of a gated GaAs two-dimensional electron gas in a perpendicular magnetic field in the regime of low carrier density and temperature where electron correlation and exchange effects are most important. For $T\simeq 0.4$ K the resonance narrows and shifts dramatically as the density is reduced below the point at which the lowest spin-split Landau level is filled. This observation provides the first demonstration of a strong influence of electron-electron interactions on the cyclotron-resonance line shape.

We report cyclotron and magnetophonon resonance experiments on GaAs-GaAlAs heterojunctions as a function of temperature. The cyclotron mass shows an anomalous increase with temperature, which we attribute to strong screening of the electron-optic-phonon interaction at low temperatures suppressing the polaron mass enhancement. The magnetophonon resonance results yield phonon frequencies significantly below the bulk GaAs LO values, suggesting that the electrons are interacting with phonons associated with the interface.

Recent determinations of the volt and the quantized Hall resistance at the Australian National Measurement Laboratory have yielded values having sub-ppm uncertainties for a number of important fundamental constants. The direct experimental results are 2e/h=483.597 90(15) THz ${\mathrm{V}}^{\mathrm{-}1}$ and h/$e^2$=25 812.809 9(20) Ω, both in SI units. Derived values are given for the electron charge, Planck’s constant, the magnetic flux quantum, and the inverse fine-structure constant.

A new experimental search with the Crystal Box detector shows no evidence for the lepton-family-number–nonconserving decay ${\mu }^{+}$→$e^{+}$γγ. This corresponds to an upper limit for the branching ratio of Γ(μ→eγγ)/Γ(μ→eνν¯)<7.2 ×${10}^{\mathrm{-}1}$ (90% confidence level), an improvement of more than 2 orders of magnitude in sensitivity.

We report on the first search with virtual photon-photon collisions for narrow, neutral resonances with even C parity in the mass range 4.5<W<19 GeV. The data were obtained via the process $e^{+}$$e^{\mathrm{-}}$→$e^{+}$$e^{\mathrm{-}}$${\gamma }^{\mathrm{*}}$${\gamma }^{\mathrm{*}}$→e ${}_{}{}^{+}{}_{}{}^{}e_{}^{\mathrm{-}}{}_{}{}^{}$R with both the scattered $e^{+}$ and $e^{\mathrm{-}}$ detected. We find upper limits (95% confidence level) for the partial decay width of a resonance into two photons, ranging from 50 keV at W=4.5 GeV to 10 MeV at W=19 GeV. These limits constrain theoretical models involving neutral composite bosons.

Emulsion chambers were used to measure the transverse momenta of photons or ${\pi }^0$ mesons produced in high-energy (≥1 TeV/amu) cosmic-ray nucleus-nucleus collisions. A group of events having large average transverse momenta have been found which apparently exceed the expected limiting values. Analysis of the events at early interaction times, of the order of 1 fm/c, indicates that the observed transverse momentum increases with both rapidity density and energy density.

The simultaneous direct mass measurements of 21 neutron-rich nuclei ranging from ${}_{}{}^{19}{}_{}{}^{}\mathrm{C}$ to ${}_{}{}^{37}{}_{}{}^{}\mathrm{P}$ have been performed with a new type of recoil spectrometer. The masses of ${}_{}{}^{19}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27–28}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{32–34}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{36}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{37}{}_{}{}^{}\mathrm{P}$ have been determined for the first time. No evidence of an increase in the two-neutron separation energy as noted for ${}_{}{}^{31–32}{}_{}{}^{}\mathrm{Na}$ is observed for ${}_{}{}^{30–32}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{32–34}{}_{}{}^{}\mathrm{Al}$.

Partial decay schemes for the very neutron-rich nuclei ${}_{}{}^{142}{}_{}{}^{}$,144Ba and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ have been determined by the study of γ-γ coincidences in ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ fission fragments. Interlaced positive- and negative-parity levels connected by fast electric dipole transitions are observed in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ above spin 7ħ. This is similar to the situation in some light actinide nuclei, where the data have been interpreted in terms of reflection-asymmetric shapes.

We investigate the eigenvalue spectra of hydrogen Rydberg atoms in strong magnetic fields for manifestations of quantum stochasticity and find (i) a smooth transition from a Poisson-type to a Wigner-type distribution of level spacings in the range of energy where classical motion becomes increasingly chaotic, (ii) the occurrence of multiple avoided crossings, and (iii) connected with this, an extreme sensitivity of oscillator strengths, and thus of observable spectra, with respect to small variations of an external parameter, viz., the magnetic field strength.

We report the first successful application of resonant multiphoton ionization to the diagnosis of a discharge. This technique is used to measure rotational temperatures of ${\mathrm{H}}_2$ in the metastable c ${\mathrm{}}^3$${\mathrm{\Pi }}_{\mathrm{u}}^{\mathrm{-}}$ state, which are in the range of 400 to 600 K. The density of these molecules is determined by a single-photon ionization process, yielding a value of 3×${10}^9$ ${\mathrm{cm}}^{\mathrm{-}3}$ at a discharge current of 30 A. The relevance of these metastable molecules to ${\mathrm{H}}^{\mathrm{-}}$ production in hydrogen discharges is discussed.

Three-dimensional particle simulations of collisionless drift waves in sheared magnetic fields were performed in order to determine the nonlinear behavior of inverse–electron-resonance dynamics in the presence of thermal fluctuations. It is found that stochastic electron diffuision in the electron-resonance overlap region can destabilize the drift-wave eigenmodes. Numerical evaluations based on a nonlinear electron-resonance broadening theory give predictions in accord with the frequency and growth rates found in the simulation of short-wavelength modes (${\mathrm{k}}_{\mathrm{y}}$${\mathrm{\rho }}_{\mathrm{s}}$≳1).

Polarization-dependent surface extended x-ray absorption fine-structure (SEXAFS) measurements on the O(2×1)/Cu(110) system show that every second [001] Cu row on the surface is missing, thus excluding the buckled-row model for the reconstruction. A SEXAFS amplitude comparison clearly favors the missing-row over the sawtooth model. It also provides evidence for a strong anisotropy of both the surface mean free path and the surface Debye-Waller factor.

A new high-frequency and short-wavelength collective mode specific to binary liquid mixtures with large mass difference is observed in a computer simulation of ${\mathrm{Li}}_{0.8}$${\mathrm{Pb}}_{0.2}$ and discussed within the framework of the Mori-Zwanzig formalism. The mode shows linear dispersion in a wave-number regime 0.1 A${\mathrm{̊}}^{\mathrm{-}1}$≤q≤0.6 A${\mathrm{̊}}^{\mathrm{-}1}$, but its propagation velocity is higher than the ordinary sound velocity by more than a factor of 3. Its attenuation is only weakly q-dependent in contrast to the damping of ordinary sound. In ${\mathrm{Li}}_{0.8}$${\mathrm{Pb}}_{0.2}$ ‘‘fast sound’’ entails motion of the lighter atoms only.

Vacancy jump rates in fcc solids are calculated accurately on the basis of the short-memory–augmented rate theory. We find that the observed isotope and return jump effects are both dominated by a small temperature-dependent fraction of highly anharmonic trajectories in which strong hard-core interactions occur.

We have prepared tunnel junctions on superconducting ZrN thin films using the natural oxide as a tunnel barrier. In the superconducting density of states we observed the phonon-induced structures due to the acoustic and optical phonons. The tunnel data could be analyzed by the McMillan-Rowell procedure without the need to correct for proximity effects. From the resulting Eliashberg function it was concluded that the optical phonons are coupled slightly more strongly to the electrons than the acoustic phonons.