The fusion of ${}_{}{}^{80}{}_{}{}^{}\mathrm{Se}$+${}_{}{}^{80}{}_{}{}^{}\mathrm{Se}$ has been studied near and just below the Coulomb barrier. High angular momentum components were observed by measurement of $\gamma$-ray multiplicity distributions for the decay of the evaporation residues.

${\pi }^0$ production cross sections are calculated with use of a Boltzmann master equation which assumes a nucleon-nucleon collision relaxation mechanism for the reaction of 35-MeV/nucleon ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ with ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$ targets, and for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at energies of 60, 74, and 84 MeV/nucleon. Results support a nucleon-nucleon collision mechanism as one possible interpretation of experimental yields.

Differential elastic high-energy electron-scattering cross sections for C${\mathrm{O}}_2$ have been measured and, with use of earlier total results, inelastic cross sections were derived. A comparison with the independent-atom model, molecular Hartree-Fock, and configuration-interaction calculations reveals the importance of the electron correlation for a first-order density property (elastic scattering) and a second-order one (inelastic scattering). Integral quantities such as the potential-energy differences $\Delta V_{\mathrm{ee}}\left(\mathrm{exchange}\right)$ and $\Delta V_{\mathrm{ne}}+\Delta V_{\mathrm{ee}}\left(\mathrm{Coulomb}\right)$ are determined. In addition, the first precise molecular structure of a molecule has been derived from only elastic data.

We examine phase conjugation in liquid suspensions of microparticles in the saturation limit. If the polarizations of the pump waves are orthogonal, new states should appear discontinuously in a pairwise fashion which are stable at the bifurcation point. These states correspond to different intensities of the conjugate and amplified probe waves. Analysis indicates that this effect should be experimentally accessible in the microwave region utilizing 10-μm microspheres.

A wetting fluid is displaced at very low flow rate by a nonwetting fluid in a 250 000-duct, transparent, etched network. The structure formed by the injected fluid is ramified and the scale invariance is described by a measured fractal dimension $1.80<D<\mathrm{}1.83\mathrm{}$. This value agrees with theoretical results of invasion percolation with trapping.

Low reflectivity of stimulated Brillouin scattering is shown to result from wave-interaction incoherency caused by the ion sound-wave nonlinearity. The Brillouin reflectivity is numerically found to display a chaotic time evolution at laser fluxes below those at which ion sound-wave harmonic generation takes place. At these fluxes, the scattered light exhibits a spiky frequency spectrum. Scaling laws for the reflectivity are given.

Experimental studies of light scattering in the tricritical region of mixtures of ethane with heavier hydrocarbons show that the intensities and correlation lengths do not satisfy the asymptotic form of the Griffiths first sum rule. Both sums increase sharply rather than approaching zero as the tricritical point is approached, indicating that either (a) there is a nonclassical divergence in the sums, or (b) many terms must be retained in a power series for the coupling "constant." Similar results have been found in a reanalysis of earlier experiments.

Magnetically generated superflows were observed in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A_1$ phase at pressures of 22.3 to 25.9 bars in magnetic fields of 3.7 to 5.5 kG. A two-fluid model is used to calculate the magnitude of the magnetic fountain effect. Critical-velocity effects were observed for sufficiently high flow rates. The critical velocity in the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A_1$ phase was found to be 0.21 mm/sec in the reduced temperature range 0.0004 to 0.008. A threshold field gradient for the magnetic fountain effect was observed in part of the $A_1$ phase and may be evidence of fluctuations above $T_{c2\mathrm{}}$.

We propose the use of third sound in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films on a disordered substrate as a system for the study of Anderson localization in two dimensions. Quantitative predictions for the localization length are made with use of the self-consistent diagrammatic theory of localization. Dramatic effects are predicted in an experimentally accessible regime.

The photofragmentation spectra of ${{\mathrm{Si}}_n}^{+}$ for $n=2\mathrm{} \mathrm{to} 12$ have been obtained in an apparatus that produces, isolates, and fragments ionic clusters on a mass-resolved basis. The most prominent species are found to be ${\mathrm{Si}}_6^{+}$ and ${\mathrm{Si}}_{10}^{+}$. The fragmentation data are shown to be consistent with a microcrystal model of cluster geometry for ${{\mathrm{Si}}_n}^{+}$.

A unique assignment of both the orientation and the adsorption site of formate (HCOO) on Cu(110) has been made by analysis of near-edge and extended x-ray-absorption fine structure. The species lies with its molecular plane perpendicular to the surface, aligned along the [$1\overline{1}0$] directions, and on top of the copper atoms of the outermost layer; the oxygen atoms almost bridge two copper atoms with an average Cu-O bond length of 1.98±0.07 Å, essentially identical to that in bulk copper formate.

We report the first self-diffusion measurements of water-in-oil microemulsions done with fringe-pattern photobleaching-recovery techniques. These measurements give evidence of the onset of droplet aggregation which can be fairly distinct from the percolation threshold where an infinite aggregate is formed. Our results show that in some cases spherical droplets may not exist even at very low water-volume fractions. Above the observed onset, the self-diffusion coefficient reaches a nonzero limit value, reflecting the dynamical aspect of aggregation in these media.

The quantized quasiparticle spectrum associated with the bending in an $\hat{l}$ texture is most readily seen in the ultrasonic attenuation at low temperatures (say $\frac{T}{T_c}\lesssim 0.3$). The attenuation coefficient has a strong frequency dependence for $\hslash \omega ={\Delta }_0{\left(2\mathrm{}\epsilon \right)}^{\frac{1}{2}}[p^{\frac{1}{2}}+{\mathrm{}(p+1\mathrm{})\mathrm{}}^{\frac{1}{2}}]$, where $p$ is an integer and $\epsilon$ is a bending parameter of the order of ${10}^{-3\mathrm{}}$ typically. We propose a few experimental setups where the necessary texture is created.

The prototypical W(001) structural phase transition is investigated by all-electron, frozen-phonon, total-energy calculations. The strong coupling between surface states and the ${\overline{M}}_5$ phonons plays a decisive role in favoring the reconstructed $c(2\mathrm{}\times 2)$ structure with a lateral $〈110〉$ zig-zag displacement of 0.18±0.01 Å (in excellent agreement with experiment) and no interlayer relaxation. The transition from the (1 × 1) into the $c(2\mathrm{}\times 2)$ phase proceeds over a very flat region of the energy hypersurface and suppresses the relaxation.

We estimate the flux of neutrinos produced by protons accelerated by the compact partner in Cygnus X-3. Such neutrinos are produced in collisions with the atmosphere of the companion, and there can be substantial modulation due to absorption in the companion. The resulting flux of upward muons induced by neutrinos in rock below an underground detector is at the level of 1 per 1000 ${\mathrm{m}}^2$ per year.

The fine-scale anisotropy of the cosmic microwave background radiation, induced by primordial scale-invariant adiabatic density fluctuations, has been studied in flat cosmological models dominated by relativistic particles from the recent decay of a massive relic-particle species. We find that, if the relic-particle species consists of massive, unstable neutrinos, there is appreciable, and probably excessive, fine-scale anisotropy in the cosmic microwave background.

The equation of state of the fluid phase of the classical hard-sphere system in infinitely many dimensions has been obtained exactly. Only the first two virial coefficients are nonvanishing. The upper bound for the coefficients of the Mayer series for nonnegative interaction potentials is reached by this system.

We present evidence that hydrogen dissolved in metallic alloys can be considered as a realization of a lattice gas with a random internal field and random bonds. The predictions of this model are in good agreement with experimental phase diagrams and results of diffuse x-ray scattering from microscopic density fluctuations of hydrogen in ${\mathrm{Nb}}_{1-x}{\mathrm{Mo}}_x$ alloys.

Variational solutions are found for the Dirac equation for various potentials. The stationary energy values correspond to saddle points in parameter space. This has the effect of limiting both negative- and positive-energy contributions. Comparison with exact numerical results shows good agreement for the energy and for other expectation values.

The production of $\Lambda$ hyperons in $e^{+}{e}^{-}$ annihilation has been measured as a function of their total momenta, transverse momenta, and the event thrust. The total production rate is 0.213±0.012±0.018 $\Lambda$ or $\overline{\Lambda }$ per hadronic event. The observation of correlations in rapidity and angles for events with two detected $\Lambda$ decays supports fragmentation models with local baryon-number compensation.