We propose a growth model for deposition of thin amorphous films by the sputtering technique. For small values of the diffusion constant, the film develops a self-similar mountain landscape. As the diffusion constant is increased a regime is reached where growth of compact flat films is possible up to a critical height. Further deposition leads to surface roughening.

The diffusion rate of muonium in an insulator, KCl, has been determined from measurements of muon spin relaxation induced by motion in the presence of nuclear hyperfine interactions. The crossover from stochastic to coherent hopping occurs at about 70 K, as evidenced by a dramatic rise in the hop rate at lower temperatures. The coherent hop rate rises much more rapidly with decreasing temperature than for muon diffusion in metals, as predicted by current theories on the diffusion of light interstitials in the absence of conduction electrons.

A tilt $\theta$ of the optic axis linear in transverse electric field was observed in a surface-stabilized chiral nematic liquid crystal. The electroclinic constant $\frac{d\theta }{\mathrm{dE}}$ was found to exhibit significant pretransitional behavior on approaching the nematic-smectic-$A$ transition temperature from above. A simple theoretical discussion involving coupled order parameters is presented.

Recent Monte Carlo studies have demonstrated the existence of positionally ordered phases in systems of monodisperse, parallel hard spherocylinders. We present an excluded-volume theory of this system which utilizes a scaled-particle treatment of dimensions possessing full translational freedom combined with a simple cell model for positionally ordered dimensions. The calculated phase diagram is in excellent qualitative agreement with the Monte Carlo results, exhibiting regions of nematic, smectic, columnar, and crystalline stability.

Mixtures of lutidine and water imbibed in porous Vycor have been studied using Raman, elastic, and quasielastic light scattering. At low temperatures, adsorption of lutidine on the internal glass surface gives rise to local composition gradients. At higher temperatures, a transition from complete to partial wetting occurs. Composition fluctuations extend over several pores, and the local chemical and geometrical randomness sets the stage for a random-field transition. The critical exponent $\beta$ associated with this latter transition is smaller than in the pure system.

It has been possible to identify two critical compositions in the IV-VI chalcogenide glassy system ${\mathrm{Ge}}_x{\mathrm{Se}}_{100-x}$ by the anomalous variations of the high-pressure electrical resistivity behavior. The first critical composition, the chemical threshold, refers to the stoichiometric composition. The second critical composition, identified recently as the mechanical percolation threshold, is connected with the structural rigidity of the material.

The use of positrons to probe thin-film pseudomorphism is presented. The first use of reemitted-positron spectroscopy to determine critical thicknesses, volume expansions, and residual lattice strains for epitaxial Ni films on Cu(100), (110), and (111) substrates is explored. The effects of the substrate surface orientation and annealing of the film are systematically investigated. The positron deformation potential of Ni, which calibrates the spectroscopy, is separately determined by thermal expansion and by pseudomorphic expansion. The two results agree but are inconsistent with theory.

Angle-resolved laser photoemission investigations of the laser-excited GaAs(110) surface have revealed a previously unobserved valley of the $C_3$ unoccupied surface band whose minimum is at $\overline{X}$ in the surface Brillouin zone. Electron population in this valley increases only as a result of scattering from the directly photoexcited valley at $\overline{\Gamma }$. With high momentum resolution, we have isolated the dynamic electron population changes at both $\overline{\Gamma }$ and $\overline{X}$ and deduced the scattering time between the two valleys.

We present the first experimental analysis of domain-wall fine structure at the surface of single-crystal iron bulk material by means of a UHV microscope with spin-polarization analysis of the secondary electrons. It is found on Fe(100) that the domain wall of a 180° Bloch wall in the bulk is terminated in a Néel-type structure at the surface. In spite of this dramatic change of the wall structure, the wall width at the surface is about the same as inside the sample. For the 180° Bloch walls we find a width of 210±40 nm.

We consider the effects of disorder in Josephson-junction arrays with an average flux quanta per plaquette $f_0$. We show that for $f_0=n+\frac{1}{2}$, positional disorder decouples the excitations responsible for the destruction of superconductivity from other excitations so that near the critical field $f_c$, the superconducting properties are described by the theory of integer $f_0$, leading to the same critical field.

Using the high-resolution Bitter-pattern technique, we have studied the vortex structure in crystals of the high-$T_c$ superconductor, Y${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$, for fields parallel to the $c$ axis. We describe the vortex pinning by twin boundaries and show that a vortex lattice develops in twin-free regions. But the results also show directly that vortices are pinned at low temperatures even in crystals which are essentially defect free. We believe this pinning must be intrinsic to the new superconductors.

Full potential, linearized, augmented plane wave, total-energy calculations predict that the breathing mode in ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ is a high-frequency mode, in agreement with experiment and contrary to previously published results. We also find the experimentally observed tilt mode to be unstable within the local-density approximation. Eight other modes were studied, and excellent agreement with experiment was found, indicating that the local-density approximation gives accurate total energies and static density response for the high-temperature superconductors.

By using a combination of hydrodynamics, scaling, and renormalization-group analysis, and a fit to the simulations of a classical rotor model, we can predict the form of the dynamic structure factor $S(\mathrm{k}, \omega )$ of a two-dimensional quantum Heisenberg antiferromagnet at low temperatures, if the zero-temperature spin-stiffness constant ${\rho }_s$ and magnetic susceptibility ${\chi }_{\perp }^0$ are known. These results should be applicable to inelastic neutron scattering in stoichiometric ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ above its Néel temperature, with only ${\rho }_s$ as an adjustable parameter.

Previous "fifth-force" experiments searched for differential acceleration of test bodies placed near terrestrial sources. Because these sources have $N\approx Z$ the results had little sensitivity to forces coupled to $B-2L=N-Z$. We searched for such forces by placing a 1-ton Pb source close to a Be/Al torsion balance. Our null results rule out (at $2\sigma$) the possibility that all previous composition-dependence results could be due to a force coupling predominantly to $B-2L$ with a range $\lambda <1000\mathrm{}$ m. We also set improved constraints on new interactions with $0.3\le \lambda \le 10$ m.

Inclusive jet production at $\sqrt{s}=1.8\mathrm{}$ TeV has been measured in the CDF detector at the Fermilab Tevatron $\overline{p}p$ Collider. Jets with transverse energies ($E_t$) up to 250 GeV have been observed. The $E_t$ dependence of the inclusive jet cross section is consistent with leading-order quantum-chromodynamic calculations, and comparison with lower-energy data shows deviations from scaling consistent with QCD. A lower limit of 700 GeV (95% confidence level) is placed on the quark compositeness scale parameter ${\Lambda }_c$ associated with an effective contact interaction.

If a fourth fermion generation exists, it is possible that the next charge $-\frac{1}{3}$ quark ($b^{\prime }$) is lighter than the top. The leading charged-current transition $b^{\prime }\to c{W}^{*}$ is expected to be strongly suppressed by mixing angles. This leads to the interesting and likely consequence that the $b^{\prime }$-quark decay is completely dominated by loop-induced flavor-changing neutral currents, which have distinctive experimental signatures. The relative importance of $b^{\prime }\to b{g}^{*}$, $b^{\prime }\to b\gamma$, and $b^{\prime }\to \mathrm{bZ}$ transitions (as well as comparisons with $b^{\prime }\to c{W}^{*}$) are explored for $b^{\prime }$ masses up to 130 GeV.

We have made wavelength measurements of the three transitions 2S-8D, 2S-10D, and 2S-12D in atomic hydrogen and deuterium to determine a new value for the Rydberg constant, $R_{\infty }=109\mathrm{}737.315709\left(18\right)\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, currently the most precise one. As reference we made use of an ${\mathrm{I}}_2$-stabilized He-Ne laser, compared to the standards of the Bureau International des Poids et Mesures. The H-D isotopic shifts have also been measured and a value for the proton-to-electron mass ratio deduced: $\frac{m_p}{m_e}=1836.152\mathrm{}59\left(24\right)\mathrm{}$.

The curvature-driven interchange mode is stabilized by spatially modulating the magnetic field lines at the plasma surface. This is effected by a high-order multipole field. No radial magnetic well is created, and axisymmetry is retained throughout most of the volume. The density, plasma lifetime, and pressure gradient increase by an order of magnitude in the stabilized plasma due to suppression of wave-induced radial transport. A model of wave stabilization by finite-Larmor-radius effects enhanced by the localization of wave fields is quantitatively established by computer simulation.

The results of computer simulations of transport of macromolecules in a disordered porous medium, represented by a network of capillary tubes with random radii, are reported. We develop a method for determining the macroscopic diffusivity $D$ which, in principle, is exact. The effects of both convection and diffusion are taken into account. We find $\frac{D}{D_{\infty }}\sim \exp (-\frac{a}{r_m})$, independent of the morphology of the medium or the microscopic transport laws, where $a$ is the effective size of the molecules, $D_{\infty }$ the diffusivity in an unbounded solvent, and $r_m$ the mean effective size of the pores, consistent with experimental data.

We consider Ising-type systems in the finite cross-section cylindrical geometry, with an interface imposed by the antiperiodic or + - boundary conditions. Closed forms are derived for the largest, asymptotically degenerate transfer-matrix eigenvalues. For rough interfaces ($0<T<\mathrm{}{T}_c$ in 2D, $T_R<T<\mathrm{}{T}_c$ in 3D), the eigenvalues are split algebraically, and the spectral gaps are governed by the surface stiffness coefficient. For "rigid" interfaces ($0<T<\mathrm{}{T}_R$ in 3D), the splitting is exponential, and determined by the step-free energy.