The difference between the $\mathrm{pp}$ and $p\overline{p}$ elastic $\frac{d\sigma }{\mathrm{dt}}\text{'}\mathrm{s}$ found at the CERN intersecting storage rings and the behavior of the $\overline{p}p$ $\frac{d\sigma }{\mathrm{dt}}$ at the CERN collider have profound implications for the high-energy behavior of hadron scattering amplitudes. The consequences are shown to be striking in the tetraelectronvolt region.

Heavy-ion fusion reactions of light and medium systems have been analyzed within a two-step compound model involving a dinucleus coupled to particle and breakup channels, as well as to the equilibrated compound nucleus. The fused configuration is reached from the entrance channel only via the dinucleus. The resulting fusion cross sections, defined as the summed particleemission cross sections from the equilibrated system, are in reasonable agreement with the data.

An oscillatory charge dependence of total electron-capture cross sections has been observed for fully stripped projectiles having charge $6<~Z<~10$ incident on H and ${\mathrm{H}}_2$ at collision energies below 3.0 keV/amu. The oscillations are attributed to the discreteness of the projectile final-state spectrum and the strong selectivity of the capture process at a given energy. Relative maxima in the cross sections occur for odd projectile charge in the case of H, and for even projectile charge in the case of the ${\mathrm{H}}_2$ target. This shift is explained in terms of a Landau-Zener curve-crossing picture of the electron-transfer collision.

We have measured the radiation emitted by 150-GeV $e^{-}$ incident along the $〈110〉$ axis of Ge crystals. The on-axis total radiated energy is 25 times larger than for nonaligned directions for 0.4-mm-thick Ge. The distribution of the radiated energy versus the angle of the electron beam yields a half-width much larger than the channeling critical angle. The on-axis results confirm the predictions of the crystal-assisted radiation theory. The Born approximation to the coherent bremsstrahlung fits the data at large angles.

It is shown that the absolute free energy of lattice spin systems can be calculated directly by a novel application of Monte Carlo sampling of finite-size dependence. Results are obtained for the two- and three-dimensional Ising models at $T_c$ and are consistent with recent finite-size scaling-theory predictions. The free energy is in excellent agreement with Onsager's exact solution for two dimensions and with series expansions for three dimensions. The $U_0$ is measured for the first time. Results are consistent with the proposed universality.

The glass transition has historically been viewed as an anomaly involving the specific heat of supercooled liquids. It is also associated with a divergence of the relaxation times for liquid rearrangements. We have developed a new spectroscopy to study the frequency dependence of the specific heat of liquids which connects these two approaches. We report measurements as a function of temperature of the distribution of relaxation times which are directly responsible for the glass transition in glycerol.

We have imaged with the tunneling microscope the microscopic surface topography of germanium layers grown by molecular-beam epitaxy on Si(111)-7×7. The surface structures corresponding to Ge(111)-$c2\mathrm{}\times 8$ and Ge(111)-7×7 are resolved. The Ge-$c2\mathrm{}\times 8$ structure is shown to consist of a coherent combination of two simpler units both of which exist independently on the surface. The associated phase boundaries are illustrated. The Ge 7×7 structure is shown to be similar to that obtained for Si(111). Defects in the cell are also imaged.

A coherent-inelastic-neutron-scattering experiment was performed on liquid ${\mathrm{D}}_2$O at room temperature. We observe for the first time the collective high-frequency sound mode as predicted by computer molecular-dynamics simulations. We interpret the excitation to be a mode propagating within the hydrogen-bonded patches existing in liquid water, and distinct from the ordinary sound wave.

We report the first measurements of the critical exponents of a phase transition at the surface of a clean metal, the Au(110) (1 × 2) ↔ (1 × 1) transition. The exponents $\beta$, $\gamma$, and $\nu$ and the amplitudes were measured by LEED and place the phase transition in the two-dimensional Ising universality class. The critical scattering is observed to peak above $T_c$, signaling the breakdown of the Ornstein-Zernike theory, and is in numerical accord with predictions of Fisher and Burford.

We present here a general framework to produce quasiperiodic tilings and more general quasiperiodic patterns in $n$ dimensions corresponding to a finite number of local neighborings around each point. In particular, we give simple descriptions of the Penrose tilings of the plane and of a tiling of the three-dimensional space which exhibits an icosahedral symmetry. The Fourier transform of this last pattern is derived and shows a striking similarity with the electron-diffraction images obtained for a recently discovered alloy of Al and Mn.

A simulation of the magnetoresistance of very small wires shows sample-specific, aperiodic structure due to the non-self-averaging nature of quasi-one-dimensional conductors in this size range. This explains earlier failures to observe flux-periodic magnetoresistance in very small rings. Analysis of the temperature and size dependence of the effect gives good agreement with experiment. A prediction is made for the experimental conditions in which oscillations periodic with flux $\frac{\mathrm{hc}}{e}$ will be observed.

Magnetoresistance oscillations periodic with respect to the flux $\frac{h}{e}$ have been observed in submicron-diameter Au rings, along with weaker $\frac{h}{2e}$ oscillations. The $\frac{h}{e}$ oscillations persist to very large magnetic fields. The background structure in the magnetoresistance was not symmetric about zero field. The temperature dependence of both the amplitude of the oscillations and the background are consistent with the recent theory by Stone.

Strongly enhanced two-dimensional ferromagnetic moments are predicted for $3d$ bcc transition metals as overlayers and/or sandwiches and superlattices with Au and Ag. These range (in Bohr magnetons) from (i) 3.70 for Cr/Au(001), 2.96 for Fe/Ag(001), and 2.0 for V/Ag(001) for the overlayers, to (ii) 3.10 for the Au/Cr/Au sandwich and 2.95 for the Cr/Au superlattice, and to (iii) 3.1 for Cr on Fe/Au(001) and 2.30 for Fe on Cr/Ag(001). Surprisingly, a sizable moment (0.14${\mathrm{\mu }}_{\mathrm{B}}$) is induced onto neighboring Au atoms. The noble metals play an optimal role as an almost ideal substrate which allows two-dimensional magnetism to occur.

The electronic properties of a ferromagnetic Fe monolayer epitaxially adsorbed on a Ag{100} substrate have been computed fully self-consistently. The minority $d$-band spin states of the Fe overlayer were found to be separated energetically from the majority-spin band. The magnetic moment per overlayer atom is 3.0${\mathrm{\mu }}_{\mathrm{B}}$, 36% larger than that of bulk iron.

Randomly placed impurities that alter the local exchange couplings, but do not generate random fields or destroy the long-range order, roughen domain walls in Ising systems for dimensionality $\frac{5}{3}<d<\mathrm{}5\mathrm{}$. They also pin (localize) the walls in energetically favorable positions. This drastically slows down the kinetics of ordering. The pinned domain wall is a new critical phenomenon governed by a zero-temperature fixed point. For $d=2\mathrm{}$, the critical exponents for domain-wall pinning energies and roughness as a function of length scale are estimated from numerically generated ground states.

Measurements of the tunneling rate $\Gamma$ out of the zero-voltage state for several Nb edge junctions with differing shunt capacitances are described. At zero temperature, increasing the shunt capacitance lowers $\Gamma$ in agreement with dissipative calculations of the macroscopic-quantum-tunneling rate. As temperature increases, $\ln \left[\frac{\Gamma \mathrm{}\left(T\right)\mathrm{}}{\Gamma \mathrm{}\left(0\right)\mathrm{}}\right]\propto T^2$ as recently predicted.

The initial dissociative chemisorption probability of C${\mathrm{H}}_4$ on a W(110) surface is found to increase by ∼${10}^5$ on raising of the C${\mathrm{H}}_4$ incident translational energy, reaching a value of ∼0.2 at 100 kJ/mole. This is by far the largest such effect (by ∼${10}^3$) reported to date and is consistent with a mechanism dominated by quantum tunneling, a conclusion further supported by measurements for C${\mathrm{D}}_4$.

Lower limits for the neutrino mass are obtained if one flavor of neutrino is predominantly responsible for the dark matter in galaxies. From rotation curves of spiral galaxies, it is found that the neutrino mass must exceed $35h^{\frac{1}{2}}$ eV (where $h$ is the Hubble constant in units of 100 km ${\mathrm{s}}^{-1\mathrm{}}$ ${\mathrm{Mpc}}^{-1\mathrm{}}$) if the velocity distribution of halo neutrinos is isotropic. If radial dispersion dominates, limits are slightly weakened. These results do not rely on a specific form of the phase-space distribution of halo neutrinos.

Operationalistic definition of the dimension of space-time leads to the possibility of its experimental determination. Several reasons may be given for the fractional dimension of space-time to be slightly smaller than four, yielding a finite quantum electrodynamics. Comparison between the best experimental values for the electron $g-2\mathrm{}$ factor and theoretical prediction gives the value 4- (5.3±2.5)×${10}^{-7\mathrm{}}$ for the dimension of space-time.

Models of self-avoiding random surfaces with chemical potentials for topological quantities in three and four dimensions are investigated by Monte Carlo methods. We explore the phase diagrams and find first- and second-order transition lines and triple points.