Thomson backscattering of C${\mathrm{O}}_2$-laser radiation is used to determine the parallel momentum spread of a 1-kA/${\mathrm{cm}}^2$, 700-kV magnetized electron beam, emitted from a cold cathode in an apertured diode. The beam is found to be suitable for Raman free-electron-laser applications: a normalized momentum spread of (0.6±0.14)% was obtained for the inhomogeneous broadening; it is also found that the use of an undulator will cause an increase of the broadening.

The inelastic He/Ag(111) cross section has been evaluated in the one-phonon distorted-wave Born approximation. The authors use an atom-surface potential made up by a repulsive part derived from a superposition of atomic charges and by the attractive van der Waals interaction. The surface phonon density of states is evaluated within a force-constants parametrization of the bulk dynamics. By changing the surface force constants the authors are able to explain all the salient features appearing in the experimental time-of-flight spectra.

Landau-Ginzburg-Wilson symmetry analyses and Monte Carlo calculations for the classical antiferromagnetic planar ($\mathrm{XY}$) model on a triangular lattice reveal a wealth of interesting critical phenomena. From this simple model arise a zero-field transition to a state of long-range order, a new mechanism for spin disordering, and a critical point associated with a possible new universality class.

A theoretical study of intercalation predicts stage-changing phase transitions to be continuous and to proceed via stage-disordered states. Detailed results are presented for typical donor and acceptor graphite intercalation compounds. Other systems are also discussed. A scaling rule relating stage disorder to domain size, stage, temperature, in-plane density, and charge transfer is proposed. A fundamental limit is set on the period of well staged structures. Experimental implications are discussed.

A Bonse-Hart x-ray interferometer was used to determine the (220) Fourier component of the distribution function of a chemisorbed submonolayer of bromine on a (111) silicon surface. This measurement demonstrates not only the presence of an x-ray interference field above the crystal surface of the analyzer of a Laue-case interferometer, but when coupled with Bragg-case standing-wave measurements also provides the means to determine uniquely the position of surface atoms relative to the bulk lattice.

The incommensurate phase of krypton on graphite is studied by use of the molecular-dynamics simulation technique for systems with graphite substrate dimensions comparable to present-day laboratory capabilities. At low temperature and for all coverages, honeycomb networks of "heavy" domain walls are observed for the first time. With increasing temperature, distortion from the perfect honeycomb structure becomes more prevalent, characterized by significant fluctuations from the symmetry directions, wall thickening, and wall roughening.

With the aid of a special-purpose molecular-dynamics hardware processor the authors have simulated two-dimensional Lennard-Jones systems of 10 864 particles. The asymptotic behavior of the orientational correlation function is found to be in accordance with a first-order melting transition.

A molecular model of field-dependent photogeneration is presented. The model, diffusion on a lattice in a combined Coulomb and external dc field, is solved exactly. The solution for the quantum efficiency $\eta$ has a larger range of applicability than the continuum theory to which it can be compared in the infinite-sink case. It is shown that $\eta$ can vary greatly with small variation of key molecular parameters and that the high-field limit of $\eta$ is controlled by the same molecular properties which determine its field dependence.

Strong polar-angle dependence has been observed in $\mathrm{KVV}$-Auger spectra of adsorbed molecules. These angular effects are caused by the anisotropy of the Auger matrix element and can be explained by simple symmetry arguments. It is shown with the example CO on Ni(100) that molecular Auger spectra can be largely understood with use of nothing but the present angular results and experimental one-electron binding energies. Information about the adsorbate orientation as well as about the screening mechanism can also be obtained.

Electrical behaviors at two single-crystal metal-semiconductor interfaces are studied. Schottky-barrier heights of Ni${\mathrm{Si}}_2$ layers grown under ultrahigh-vacuum conditions on $n$-type Si(111) are found to be 0.65 and 0.79 eV for type-$A$ and type-$B$ epitaxial systems, respectively. These results are compared with the proposed theoretical models of Schottky barriers.

Simple physical considerations of local charge neutrality suggest that near a metal-semiconductor interface, the Fermi level in the semiconductor is pinned near an effective gap center, which is simply related to the bulk semiconductor band structure. In this way "canonical" Schottky barrier heights are calculated for several semiconductors. These are in excellent agreement with experiment for interfaces with a variety of metals.

Ce${\mathrm{Cu}}_2$${\mathrm{Si}}_2$ single crystals prepared with an excess of Cu exhibit low residual resistivity ${\rho }_0$, low susceptibility $\chi$, small unit-cell volume $V$, and bulk "heavy-fermion" superconductivity below 0.65 K, while crystals grown from stoichiometric melt show higher ${\rho }_0$ and $\chi$, larger $V$, but no superconductivity. Ce${\mathrm{Cu}}_2$${\mathrm{Si}}_2$ behaves as an $s$-state superconductor with strongly temperature-dependent pair breaking and almost isotropic Fermi surface.

An analytic solution of the fluctuating diffusion equation with $k$-dependent diffusion constant and equilibrium structure factor for a suspension of strongly interacting 2340-Å colloidal particles is used to compute intensity plots for light-scattering experiments on sheared suspensions. The resulting structure factor is highly anisotropic, has a very nonlinear dependence on the shear rate, and shows a number of interesting features arising from the very wave-vector-dependent way in which the shear disorders the suspension.

An upper bound is given for the maximum number, $N_c$, of negative particles (fermions or bosons or a mixture of both) of charge $-e$ that can be bound to an atomic nucleus of charge $+\mathrm{ze}$. If $z$ is integral then $N_c<~2z$. In particular, this is the first proof that ${\mathrm{H}}^{--}$ is not stable. For a molecule, $N_c<~2Z+K-1$, where $K$ is the number of atoms in the molecule and $Z$ is the total nuclear charge.

With use of a novel Monte Carlo method suited for the study of surface phenomena, the authors have investigated a three-dimensional Ising model with modified surface exchange. The results verify the scaling behavior of the magnetization profile and confirm and extend renormalization-group predictions. The surface-layer magnetization exponent is ${\beta }_1=0.78\mathrm{}\pm 0.02$ except at the "special" (multicritical) transition where ${{\beta }_1}^m=0.175\mathrm{}\pm 0.025$ and the crossover exponent is $\varphi =0.56\mathrm{}\pm 0.04$.

The Einstein equations describing gravitational fields in vacuum are written as a compact exterior system of spinor-valued forms. A second system of equations is given, such that their integrability conditions are satisfied by virtue of the Einstein equations. This suggests the possibility of integrating the field equations by means of an inversetype procedure.

The cross section for radiative capture of protons by monopoles is calculated by the use of bound-state and scattering wave functions obtained with the Kazama-Yang Hamiltonian, i.e., with a pointlike proton. For proton velocities $\beta ={10}^{-5\mathrm{}}-{10}^{-3\mathrm{}}$, the cross sections for capture into the lowest bound states, with binding energies of 938 MeV, 263 keV, and 105 eV, are found to be of the order of ${10}^{-28\mathrm{}}$ -${10}^{-26\mathrm{}}$ ${\mathrm{cm}}^2$. For the state with binding energy of 263 keV, the capture length in water is found to be $170{\left(\frac{\beta }{{10}^{-4\mathrm{}}}\right)}^{0.48}$ m. Observation of photons from the capture process would indicate the presence of monopoles.

The longitudinal polarization of the muon emitted from the $K^{+}\to {\mu }^{+}\nu$ decay was measured to search for the right-handed weak currents in the strangeness-changing process. The polarization was determined to be -0.970±0.047, which is consistent with the $V-A$ hypothesis.

Angular distributions of the deuteron tensor polarization, $t_{20}$, in $\pi -d$ elastic scattering at pion energies of 180, 220, and 256 MeV and an excitation function at ${{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}}^{\pi }\approx 144°$ have been measured. The results suggest that all published calculations fail to include true pion absorption properly in the treatment of the $\pi \mathrm{NN}$ system. No rapid angular or energy dependence was found near pion energies of either 134 or 256 MeV, where other experiments have suggested the existence of dibaryons.

With a new detection method, the upper limit on the time-reversal-noninvariant triple angular correlation $\frac{\overrightarrow{\mathrm{J}}·({\overrightarrow{\mathrm{p}}}_e\times {\overrightarrow{\mathrm{p}}}_{\nu })}{E_e{E}_{\nu }}$ in the nuclear decay ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ → ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ + $e^{+}+\nu$ has been reduced. Polarized ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ atoms from an atomic beam are captured in a holding cell, where the decay positrons and recoil ions are observed. The new value for the asymmetry parameter for this correlation is $D=0.004\mathrm{}\pm 0.0008$, which is consistent with time-reversal symmetry.