Although many examples of pattern formation resulting from chemical reactions at liquid interfaces are known, few have been studied in detail. We report a quantitative study of patterns formed by the photoproduction of ${\mathrm{Fe}}^{2+}$ and its subsequent reaction to form Turnbull's Blue. The experiment leads to the postulation of a mechanism in which autocatalysis is enhanced by double diffusion. The phase diagram contains a line of phase transitions whose critical behavior is discussed.

The chemisorption energy and equilibrium configuration have been calculated for K adsorbed on Cu(110), by the effective-medium theory. At low coverages K is found to stabilize the (1×2) missing-row reconstructed surfe, whereas it stabilizes the unreconstructed structure at higher coverages. The calculations form the basis for a general understanding of why adsorbed alkali-metal atoms induce a (1×2) reconstruction of fcc (110) surfaces.

Scanning tunneling microscopy has been used for real-space imaging of the initial interaction of palladium with the Si(111)-(7×7) surface at room temperature. The nucleation of silicide is spatially localized and occurs only in the faulted half of the (7×7) unit cell. Large-scan-area images have been statistically analyzed to determine the subsurface extension of the silicide nuclei and the nature of growth as a function of coverage and island size. Steps are found to have no influence on the nucleation at this temperature.

An extended scaling description of the cluster size distribution $N_s\mathrm{}(t,k)\mathrm{}$ in time-dependent coagulation-fragmentation processes ($k$ is a small breakup rate constant) is presented as $N_s\mathrm{}(t,k)\mathrm{}\sim s^{-2\mathrm{}}h(s{k}^y,t{k}^x)$) and its validity is confirmed by computer simulations. This scaling form includes the scaling description of irreversible and steady-state processes as limiting cases for both short and long times compared to a crossover time $\tau \mathrm{}\left(k\right)\mathrm{}\sim k^{-x}$. A mean-field theory is analyzed and its limits of validity are explored.

New experimental data for the refractive-index behavior in the homogeneous phase below the lower critical solution point in critical-composition liquid mixtures of triethylamine and water are presented. From a comparison with existing density data it is concluded that the critical anomaly in the refractive index includes an intrinsic effect opposite in sign to the density contribution.

Fractal, dendritic patterns with invariant distributions which are harmonic measures are represented by Julia sets of polynomial mappings. The equipotential lines around such patterns are obtained, leading to analytic estimates of the minimal and maximal scaling exponents of the $f\left(\alpha \right)$ function of the harmonic measure. These and physical stability arguments rationalize the shapes of diffusion-limited aggregates.

The sticking coefficient of thermal neon atoms on a flat Ru(001) surface ($T_s=7\mathrm{}$ K) is found experimentally to be very low and strongly dependent on gas temperature (1×${10}^{-3\mathrm{}}$ to 8×${10}^{-2\mathrm{}}$ for $T_g$ from 600 to 30 K) on the clean surface, and to increase strongly with coverage to about 0.7. The zero-coverage values are incompatible with classical mechanical theory, irrespective of assumed interaction parameters, requiring substantial zero-phonon scattering. Calculations treating the energy transfer to phonons quantum-mechanically can reproduce the data with reasonable parameters.

Bulk nucleation of crystalline Si at a supercooling of 505 K was observed following pulsedlaser-induced melting of thin films. If the nucleation was homogeneous, the estimated nucleation rate of ${10}^{29}$ events/${\mathrm{m}}^3$ · s implies a liquid-Si-crystalline-Si interfacial energy of 0.34±0.02 J/${\mathrm{m}}^2$. In addition, observation of crystalline nucleation bounds the interface energy between amorphous Si and liquid Si to be > 0.20 J/${\mathrm{m}}^2$. This laser melting technique is applicable to nucleation studies in a wide variety of materials.

We explain the anomaly in the lattice constants of the series Ce${\mathrm{Fe}}_2$-Ce${\mathrm{Ni}}_2$ quantitatively in terms of $3d-4f$ hybridization rather than a valence change. Ce${\mathrm{Fe}}_2$ is calculated to be magnetic and is the first Ce compound for which self-consistent energy-band calculations yield the correct total moment (${2.4}_{\mathrm{\mu }\mathrm{B}}$/formula unit) including a contribution of ${-0.4\mathrm{}}_{\mathrm{\mu }\mathrm{B}}$ from the $4f$ electrons. The calculated magnetization density and spin-resolved density of states, which are unique to itinerant-electron theory, may be verified in detail by magnetic form-factor and spin-polarized photoemission measurements.

Scanning tunneling microscopy is used to determine the atomic structure, charge state, and electronic energy spectrum of isolated Si dangling-bond defects at the Al/Si(111) surface. Si adatoms substituting for Al in the first atomic layer give rise to a dangling-bond defect state near -0.4 eV which is strongly localized in space. Tunneling spectra and local band-bending measurements are inconsistent with simple one-electron band theory and demonstrate the importance of many-electron effects.

We generalize a type of variational wave function introduced by Kasteleijn and Marshall, to include long-range correlations and nonbipartite lattices. We find the lowest-energy wave function in a three-parameter space for both the square- and triangular-lattice spin-½ Heisenberg antiferromagnets. This produces useful upper bounds on the ground-state energies of these systems. The wave functions are completely explicit, so that precise estimates of expectation values are readily obtained by Monte Carlo techniques. It appears that the antiferromagnet has long-range magnetic order on the triangular lattice, as well as on the square lattice.

The two-probe conductance of narrow (≃100 nm) silicon inversion layers at magnetic fields above $B\simeq 4$ T is found to be anomalous in several ways. The magnetoresistance is negative and very large; the conductance at high $B$ rises with carrier density in a series of steps; each step disappears at a separate temperature. The results suggest that new many-body effects result from quasi one-dimensional confinement.

Bulk superconductivity is reported in ${\mathrm{Tl}}_2$${\mathrm{Ca}}_2$${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{x}}$ with a transition to zero resistance at ≃ 125 K, the highest transition temperature ($T_c$) yet found. Transmission electron spectroscopy shows that the unit cell is body-centered tetragonal and contains trilayer Cu perovskitelike units separated by bilayer Tl-O units. $T_c$ in this material varies from 118 to 125 K depending on preparation conditions. A high density of perovskitelike bilayer intergrowths are observed in the 118-K material, which we speculate result in the decreased $T_c$. A second structure containing only bilayer perovskitelike units—${\mathrm{Tl}}_2{\mathrm{Ca}}_1{\mathrm{Ba}}_2{\mathrm{Cu}}_2{O}_x$—is a bulk superconductor with $T_c$ ranging from 95 to 108 K.

We report the first observation of the incremental charging of single isolated small particles, which act as a common electrode in a series configuration of two small-capacitance tunnel junctions. The steplike structures in the $I-V$ characteristic, due to the quantization of the charge on the small particle, can be well described by a Monte Carlo simulation. We discuss the observation of an apparent bistability and of discrete voltage shifts of the step structure, possibly induced by the ionization of single impurity states in the oxide layer.

Phonon echoes, the acoustic analog of spin or photon echoes, are observed in the superconducting ($T_c=2.6\mathrm{}$ K) metallic glass ${\mathrm{Pd}}_{30}$${\mathrm{Zr}}_{70}$ below 50 mK. The echo generation is attributed to the coherent tunneling of two-level systems of the amorphous structure. Compared to a normal conducting amorphous metal we observe a very small decay rate $T_1^{}{}_{}{}^{-1\mathrm{}}$, which directly confirms the disappearance of an electronic relaxation channel for tunneling systems in the presence of a superconducting gap.

Photolysis of C${\mathrm{H}}_3$Br on a brominated Ni(111) surface was observed. Cross-section values are reported for 0.5-, 1-, 2-, 3-, and 10-monolayer coverages. The observed cross sections and photofragment times of flight indicate that complete quenching of the photolysis does not take place, and that the photodynamics is strongly perturbed.

It is shown that Berry's phase appears in a more general context than realized so far. The evolution of the quantum system need be neither unitary nor cyclic and may be interrupted by quantum measurements. A key ingredient in this generalization is the use of some ideas introduced by Pancharatnam in his study of the interference of polarized light, which, when carried over to quantum mechanics, allow a meaningful comparison of the phase between any two nonorthogonal vectors in Hilbert space.

We derive the exact probability distribution of the winding angle of a two-dimensional self-avoiding walk around its extremities, using Coulomb-gas techniques and conformal invariance. This gives a first example of an exact full distribution in critical geometrical models. It is extended to dense and $\Theta$ self-avoiding walks.

Critical indices $\beta$, $\gamma$ $\delta$, $\nu$, etc. are defined and calculated for self-organized critical phenomena. Scaling relations are derived and checked numerically. The order-parameter exponent $\beta$ describes the spontaneous current and the relaxation to the critical point. The power spectrum has "$\frac{1}{f}$" behavior with exponent $\phi =\frac{\gamma }{\nu z}$, where $z$ is the dynamical critical exponent.

We measured the analyzing power $A$ and the spin-spin correlation parameter $A_{\mathrm{nn}}$ in medium-$P_{\perp }^2$ proton-proton elastic scattering, using a polarized-proton target and the 18.5-GeV/c Brookhaven Alternating-Gradient Synchrotron polarized-proton beam. We found sharp dips in both $A$ and $A_{\mathrm{nn}}$, which occur at different $P_{\perp }^2$ values. The unexpected sharp structure in the spin-spin force occurs near $P_{\perp }^2=2.3\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ where the elastic cross section has no apparent structure.