Consider the statistical mechanics model on the $\nu$-dimensional lattice with nearest-neighbor interaction and single spin distribution given by $\lambda {(q^2-1)}^2$, $\lambda >0\mathrm{}$. The strong-coupling region $\lambda \to \infty$ is studied, and it is shown that in the high-temperature region there is an expansion of this model in powers of ${\lambda }^{-1\mathrm{}}$ which is asymptotic to the Ising model ($\lambda =\infty$) to any order.

Measurements of ${\pi }^{\pm }p$ backward elastic scattering have been made for incident pion momenta between 30 and 90 GeV/c and for $0<-u<\mathrm{}0.5\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The momentum dependence of the cross sections is of a form expected from a simple Regge model, and the $u$ dependence of the cross sections is similar to that observed at lower momenta.

A model of strong, electromagnetic, and weak interactions is constructed in which some of the baryon-number-changing interactions usually associated with unification at large energies are relevant at ordinary momenta. In this model, $B$-meson decay always produces an antibaryon and either a ${\tau }^{+}$ or a light neutral lepton.

Evidence for spin-dependent interactions in heavy-ion reactions has been found in the inelastic scattering of 35-MeV ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ from the 1.368-MeV, $2^{+}$ state in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$. $\gamma$ rays emitted perpendicular to the reaction plane have been measured and $\mathrm{}\left|m\right|\mathrm{}$-substate populations deduced. At ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ scattering angles ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=10\mathrm{}° \mathrm{and} 21°$, probabilities for the $\mathrm{}\left|m\right|=1\mathrm{}$ population (which is equivalent to spin flip) are found to be (1.7±0.5)% and less than 0.8%, respectively.

It is shown that the fluctuation cross section for the generalized-exciton or nested-doorway model can be obtained explicitly and exactly in the limit that doorways of successive classes have very different widths, ${\Gamma }_n\gg {\Gamma }_{n+1\mathrm{}}$, and that the doorways of a given class are overlapping, ${\Gamma }_n>D_n$. The result is given in terms of experimentally observable quantities, and explicitly separates the compound and precompound contributions. It contains the results of previous, more specialized, models as limiting cases.

Theoretical results of a model of heavy-ion collisions in terms of elementary modes of excitation are presented for the reaction Kr+Pb at 610 MeV with special emphasis on the transfer of angular momentum. The angular distributions of the fragments resulting from the sequential fission of the heavy reaction partner are calculated in a semiclassical model. Conflicting experimental results reported for similar reactions are discussed and the still rather open range of possibilities in the analysis of the data is stressed.

Neutron-neutron coincidences show that the $\beta$ decay of 8.5-ms ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ is followed by the emission of two neutrons in an intensity of (9±3)%.

A model for post-collision interaction is introduced, emphasizing the adiabatic Stark mixing of autoionizing target states in the field of the receding projectile ion. Parity is destroyed as a good quantum number for the Stark-mixed states. As a consequence the angular distribution of the autoionization electrons exhibits deviation from 90° symmetry. Recent experiments on the He $2s2p{}_{}{}^1{}_{}{}^{}P$ and $2p^2{}_{}{}^1{}_{}{}^{}D$ states excited by 10-keV ${\mathrm{Li}}^{+}$ confirm this result.

Recent measurements by Heinzmann et al. of the spin polarization of photoelectrons ejected from xenon by unpolarized light are in serious disagreement with various theoretical calculations. This Letter reports an abinitio study of spin polarization with use of relativistic random-phase approximation. Excellent agreement is obtained between the present calculations and the experimental measurements by Heinzmann et al. for xenon, krypton, and argon.

Angular distributions of Xe $5s\to \epsilon p$ photoelectrons were measured with use of pulsed synchrotron radiation and a time-of-flight photoelectron spectrometer. The asymmetry parameters ${\beta }_{5s}$ differ markedly from the nonrelativistic value of 2, particularly near the Cooper minimum, in agreement with $\mathrm{jj}$-coupling models. This confirms calculations based on the relativistic random-phase-approximation model of Johnson and Cheng, establishing the importance of the interchannel coupling in $5s\to \epsilon p$ photoionization.

Electron-density profiles up to $40n_c$ have been measured for plasmas produced on glass microballoon targets irradiated by nanosecond, C${\mathrm{O}}_2$-laser pulses in the intensity range 2×${10}^{12}$ to 6×${10}^{13}$ W ${\mathrm{cm}}^{-2\mathrm{}}$. Critical-density scale lengths of ∼ 3 μm and plateau structures, including overdense bumps, have been observed. Upper-shelf densities were greater than those attributable to radiation pressure alone, possibly indicating contributions from the superthermal plasma blowoff and self-generated magnetic fields.

Noncanonical variables are used to construct a Hamiltonian for guiding-center motion in a nonuniform magnetostatic field. Lie methods are then used to obtain the pondermotive (quasistatic) Hamiltonian for the perturbation by a wave of arbitrary polarization and wave number, with spatially modualted amplitude and wave vector. The result is applied to the problem of rf stoppering in mirror confinement.

It is shown that even within the quasilinear framework, mode-coupling terms give a zero-order contribution to the growth rate at least for one-dimensional Langmuir waves.

The flow of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ is studied in a $U$-tube geometry. The current is found to saturate at a critical value, $J_{s,c}$, which is independent of driving force. The current $J_{s,c}$ scales with temperature as ${(1-\frac{T}{T_c})}^{\frac{3}{2}}$ in agreement with Ginzburg-Landau theory.

The hydrocarbon part of (${\mathrm{C}}_{10}$${\mathrm{H}}_{21}$N${\mathrm{H}}_3$)${}_2{}^{}{}_{}{}^{}\mathrm{Cd}$${\mathrm{Cl}}_4$ represents a smectic lipid bilayer exhibiting two structural phase transitions in analogy to biomembranes. Single-crystal ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR and ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ nuclear quadrupole resonance and x-ray data show that the first transition is connected with a disordering of the polar heads whereas the second represents a partial melting of the lipid chains. A Landau theory describing the melting of bilayer membranes in terms of order parameters used in the theory of liquid crystals has been constructed to explain the obtained results.

The chemical structure of thin Si${\mathrm{O}}_2$ films and Si${\mathrm{O}}_2$-Si interfaces has been investigated using high-resolution x-ray photoelectron spectroscopy. The data are consistent with a continuous random network of four-, six-, seven-, and eight-member rings of Si${\mathrm{O}}_4$ tetrahedra joined together by bridging oxygens. This distribution changes substantially within 30 Å of the Si${\mathrm{O}}_2$-Si interface. The near-interface region is comprised of ${\mathrm{Si}}_2$${\mathrm{O}}_3$, SiO, and ${\mathrm{Si}}_2$O. This structure is interpreted by means of a structure-induced-charge-transfer model.

A direct experimental test has revealed that heterojunction energy-band discontinuities are nontransitive. This result was obtained by an x-ray photoemission-spectroscopy investigation of abrupt (110) interfaces in the heterojunction series Ge/CuBr, CuBr/GaAs, and GaAs/Ge. The sum of the valence-band discontinuities for these intefaces is 0.64 ± 0.05 eV, a large deviation from the zero sum expected by transitivity.

This paper presents production and decay characteristics of 500 high-mass, high-resolution ${\mu }^{+}{\mu }^{-}$ pairs produced in ${\pi }^{-}$ Be collisions at 150 and 175 GeV/c. The data do not agree with a simple Drell-Yan production mechanism, but indicate that higher-order quantum-chromodynamic corrections must be included.

Elastic $\omega$-meson photoproduction on protons has been measured from 46 to 180 GeV. The cross section is approximately constant with photon energy and averages 1.10 ± 0.08 μb. The $t$ dependence of the differential cross section is consistent with $A$ $\exp \mathrm{}\left(\mathrm{bt}\right)\mathrm{}$, where $b=8.4\mathrm{}\pm 0.7$ Ge${\mathrm{V}}^{-2\mathrm{}}$. The photon-omega coupling constant, obtained from a normalization of hadron elastic-scattering cross sections to the photoproduction data of this experiment (with use of vector-meson dominance and an additive quark model), is $\frac{{{\gamma }_{\omega }}^2}{4\pi }=5.4\mathrm{}\pm 0.4$.

It is shown that calculability of the mixing angles in a class of $n$-generation, leftright-symmetric $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\otimes \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R\otimes \mathrm{U}\mathrm{}\left(1\right)\mathrm{}$ models restricts the fermion mass matrix to be of the form ${{\Sigma }_{m=0\mathrm{}}}^n\oplus I_m{A}_m$ with the constraint ${{\Sigma }_{m=0\mathrm{}}}^{n}m{I}_m=n$, where $A_m$ is a nonsingular $m\times m$ Hermitian or complex symmetric block containing $2m-1$ elements and $I_m$ is the number of such blocks. Such a mass matrix cannot supply $\mathrm{CP}$-invariance-violating phases.