The resistivity of an ultrathin bismuth film has been observed and analyzed according to a two-dimensional continuum percolation model. This novel approach has produced interesting results such as the critical area fraction $x_c=0.67\mathrm{}$, the critical exponent $\alpha =1.15\mathrm{}$, and other features consistent with the two-dimensional continuum model of percolation.

Measurements of the magnetic moment of TmSe show that the low-field susceptibility and the multiboundary field-temperature ($H_0-T$) phase diagram at low temperatures depend strongly on hydrostatic pressure. For ${\overrightarrow{\mathrm{H}}}_0\parallel \mathrm{}\left[100\right]\mathrm{}$ the upper transition fields increase at a rate ≃ + 1.7 kG/kbar. The magnetic properties reflect the valence changes of ${\mathrm{Tm}}^{2+}$ to ${\mathrm{Tm}}^{3+}$ as the lattice contracts, and for $P\gtrsim 20$ kbar, the Tm ion should be trivalent.

With increasing external magnetic field $H_0\parallel c$ axis, a continuous transition from single-spin to collective excitation behavior is observed in the ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$ NMR in antiferromagnetic Mn${\mathrm{F}}_2$. The low-field, nuclear-quadrupolar-split spectrum gives way to a single Lorentzian resonance as the frequency pulling increases. Just below spin-flop, well-resolved nuclear magnetostatic modes appear, whose spacings and widths scale with their electronic counterparts.

The derivatives of extremal cross-sectional areas of the Fermi surface of tungsten with respect to angular shear have been determined by simultaneous measurements of quantum oscillations in ultrasound velocity and in torque. The results are in good agreement with the predictions of a simple model in which the angular shear is assumed to produce no effect other than to distort the geometry of the crystal lattice.

Theoretical expressions have been obtained for calculating Mössbauer paramagnetic relaxation line shapes without involving the "white-noise approximation." The relaxation matrix is shown to be dependent on the hyperfine parameters and linewidth in addition to the bath parameters. The theory is used to analyze the data for ${\mathrm{Cs}}_2$NaYb${\mathrm{Cl}}_6$ and obtain values for the mean-square dipolar field and the spin correlation time.

Field-reversing electron rings, exhibiting initial axial field changes $\frac{\delta B}{B_{z0\mathrm{}}}<~170\%$, and having overall lifetimes of greater than 1300 μ sec, have been generated by injection of 2.1-MeV, 30-kA electron-beam pulses into the relativistic-electron-coil-experiment (RECE)-Christa mirror field, $B_{z0\mathrm{}}\mathrm{}\left(z\right)\mathrm{}$. These lifetimes, which are comparable with those expected from collisional diffusion of the fast electrons, constitute an improvement of more than a factor of 40 over the earlier results from RECE-Berta.

I discuss the basic ideas in applying the Monte Carlo methods to the renormalization-group study of static and dynamic critical phenomena within the framework of a kinetic Ising model. Simple calculations demonstrating these ideas are presented.

We have measured the linear polarization correlation between the two photons from the $7{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}\to 6{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\to 6{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ cascade of ${\mathrm{Hg}}^{200}$. The results were used to evaluate Freedman's version of the Bell inequality, $\delta <~0$. Our result is ${\delta }_{\exp }=+0.046\mathrm{}\pm 0.014$, in clear violation of the inequality and in excellent agreement with the quantum mechanical prediction, ${\delta }_{\mathrm{QM}}=+0.044\mathrm{}\pm 0.007$. An important feature of the experiment was the explicit measurement of the initial density matrix for the cascading atoms.

We observe in the laboratory system that within a $\theta =20\mathrm{}°$ cone around the incident proton direction, the ratio of the average charged multiplicity for proton-aluminum interactions to that for proton-proton interactions is approximately 1 and is independent of missing mass and the transverse momentum of the trigger proton.

We propose to test the validity of the multiplicative muon-number conservation law by comparing the quasielastic reactions ${\overline{\nu }}_{\mu }+e^{-}\to {\mu }^{-}+{\overline{\nu }}_e$ and ${\nu }_{\mu }+e^{-}\to {\mu }^{-}+{\nu }_e$ at ≳400 GeV. We note that the measured electron spectrum in muon decay places strong constraints on the effective Lagrangian for the ${\overline{\nu }}_{\mu }$-induced process.

We have carried out a search for neutral hadrons with masses ≳2 GeV/${\mathit{c}}^2$ and proper lifetimes ≳${10}^{-7\mathrm{}}$ sec in the $M4\mathrm{}$ neutral beam at Fermilab. The particle masses were determined from their flight time and kinetic energy. Our upper limits for the production cross section of such particles are ${10}^{-1\mathrm{}}$ to ${10}^{-3\mathrm{}}$ times those for the production of $\psi \text{'}\mathrm{s}$ by protons for comparable kinematic conditions. This is the most sensitive search to date for quasistable neutral particles with masses ≳2 GeV/${\mathit{c}}^2$.

Available data on new mesons discovered at SPEAR are sufficient to determine the spectrum of low-lying charmed mesons and to provide a complete description of the threshold structure of $R$ in the framework of the charmonium model. A number of simple tests are proposed to confirm the charm interpretation.

Elastic and total reaction cross sections for the system $\alpha$ + ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ are analyzed to obtain a limited set of potentials which are, in turn, used to calculate absolute $\alpha$ widths. Existing shell-model calculations give ${{\gamma }_{\alpha }}^2$ values three orders of magnitude smaller—and it is now most unlikely that this discrepancy is due to an uncertainty in the $\alpha$-nucleus potential.

Certain transition frequencies in the vibrational-rotational spectra of H${\mathrm{D}}^{+}$, H${\mathrm{T}}^{+}$, and D${\mathrm{T}}^{+}$ have been calculated to a high degree of accuracy. For H${\mathrm{D}}^{+}$ the differences between the calculated frequencies and the recently reported observed frequencies are less than those previously obtained and are within the error bounds of the computation.

We have measured ionization rates for selected Stark states of sodium in the range $n=12-14\mathrm{}$, $\mathrm{}\left|m\right|=2\mathrm{}$. We find that the ionization rates for the lowest Stark components of each term are in excellent agreement with values calculated for hydrogen. The systematics of ionization of the higher sublevels, however, is in serious disagreement with hydrogenic theory because of effects of level mixing.

Parylene (${\mathrm{C}}_8$${\mathrm{H}}_8$) disks have been irradiated with a 1.06-μm laser at fluxes of ${10}^{15}$-${10}^{17}$ W/${\mathrm{cm}}^2$. The spatial and temporal scattered light distributions, x-ray spatial and spectral emission properties, and ion spatial and energy distributions were measured. The results, together with two-dimensional magnetohydrodynamic code simulations, imply absorption via collective processes, laser generation of suprathermal electrons, and transport inhibition consistent with the presence of megagauss-level thermoelectric magnetic fields.

We present a simple equation of state for classical two-component ionic plasmas in a rigid, uniform background based on the numerical solution of the coupled hypernetted-chain integral equations for the pair distribution functions. The results are used to study the phase separation of pressure-ionized H-He and H-Li mixtures.

Measurements of the cross section for the reaction $e^{+}{e}^{-}\to e^{+}{e}^{-}$ (Bhabha scattering) at angles close to 90°, relative to Bhabha scattering at 4°, are reported at center-of-mass energies of 7.0 and 7.4 GeV. The results are in agreement with quantum electrodynamics, and new limits on cutoff parameters for the photon propagator are given.

A new neutral narrow meson decaying into $K\pi$ and $K\pi \pi \pi$ was recently discovered in $e^{+}{e}^{-}$ annihilation at SPEAR. Unexpected structure was observed in the recoil-mass spectrum associated with the new particle. We demonstrate that what has been seen coincides with what was expected by advocates of charm. We explain the observed suppression of $D\overline{D}$ production and the scarcity of charged $D\text{'}\mathrm{s}$. Predictions about the production of charmed hadrons not yet seen are given.

The universality of the rise of hadron multiplicities in high-energy hadron and lepton collisions is attributed to the necessity of confining quark quantum numbers in a color-guage-theory model.