This Letter reports the results of a systematic study of the current-induced noise at the superconducting transition in thin, high-resistivity films of aluminum and tin. Analysis of the noise suggests that the onset of resistance is due to discrete phase slips of magnitude less than $2\pi$. The results are discussed in terms of the vortex unbinding models of the superconducting transition in two dimensions.

Recent data on backward pion production in 0.8-4.89-GeV proton-nucleus collisions are analyzed within the scope of models where target nucleons react collectively. It is shown that the nuclear-size dependence in data is a sensitive probe of the effective target mass. The experimental results hint at a synthesis of the cluster ("fluctuon") model and the collective tube model.

This Letter predicts the existence of localized states in semiconductors associated with electrons or holes weakly bound to fractional-charge impurities, should fractional-charge particles exist in nature. The spectrum of excited states is rich enough to provide a detailed experimental signature for isolated fractional-charge particles. Theoretical estimates relevant to detection methods, sensitivity, and background signals indicate that one fractional charge per ${10}^{21}$-${10}^{24}$ nucleons might be detectable.

A theory of quark confinement is proposed which uses only the simplest of approximations. It explains persistence of quark confinement in Yang-Mills theories with gauge group SU(2) or SU(3) as a consequence of asymptotic freedom in perturbation theory and of the known phase structure of $Z\left(2\right)\mathrm{}$ and $Z\left(3\right)\mathrm{}$ lattice gauge theory. Predictions are derived which can in principle be tested by computer simulation. Some are already tested by results of Creutz. They are in good agreement.

A structure function relation sensitive to the spin of the gluon is derived for large-transverse-momentum lepton-pair production. A direct test of this relation is devised in terms of a specific angular-correlation coefficient. Calculations of this correlation function, and other angular coefficients are presented.

The $s$-wave asymptotic normalization constants $C_0$(${}_{}{}^3{}_{}{}^{}\mathrm{H}$) and $C_0$(${}_{}{}^3{}_{}{}^{}\mathrm{H}$) are calculated for the Reid soft-core potential. The Coulomb effect is taken into account for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. $C_0\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)=1.765\mathrm{}$ and $C_0\left({}_{}{}^3{}_{}{}^{}\mathrm{H}\right)=1.706\mathrm{}$ have been obtained. In ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ (${}_{}{}^3{}_{}{}^{}\mathrm{H}$), about 60% of the contribution is due to the transition from the $\mathrm{pp}$ ($\mathrm{nn}$) ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state of a pair in one set of coordinates to the $\mathrm{np}{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ state of another set.

Angular and energy correlations have been measured for $\alpha$ particles emitted in coincidence with projectilelike fragments from deeply inelastic collisions of 204-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$. Anisotropic emission of fast $\alpha$ particles is observed; however, the main results of this and similar experiments can be reproduced by model calculations which assume the $\alpha$ particles are evaporated from fully accelerated fragments and take the angular distribution of projectilelike fragments into account.

The angular distribution of Auger electrons emitted in the decay of molecular $K$-shell vacancies created by photoabsorption is predicted to be a direct probe of the anisotropy of molecular photoabsorption. The $\sigma \to \pi$ discrete absorption and the $\sigma \to \sigma$$f$-wave shape resonance in ${\mathrm{N}}_2$ and CO are given as examples.

This Letter presents the first application of the Schwinger variational principle for multichannel scattering. Results are presented for an exactly soluble two-channel model problem. The accuracy and convergence of the Schwinger variational principle are shown to be extremely good and superior to those of other variational methods.

This Letter presents computer simulations of the reflection and heating due to stimulated Raman scattering of intense laser light in large regions of underdense plasma. The heated electron distribution is approximately a Maxwellian of temperature $\frac{1}{2}{m}_e{v_p}^2$. A simple model of the reflection is presented. Forward Raman scattering was also observed producing extremely energetic electrons. Finally, two-dimensional simulations showed sizable Raman scattering coexisting with heating by the $2{\omega }_{\mathrm{pe}}$ instability. Raman scattering may cause a preheat problem with large laser-fusion-reactor targets.

A density cavity at the upper-hybrid resonance layer has been observed in the saturated stage of the trapped electrostatic field when a high-power microwave of the extraordinary mode is injected into an afterglow plasma column in a uniform magnetic field. The results can be explained by the modulational instability at the upper-hybrid frequency and the formation of an upper-hybrid soliton.

At large densities or large distances from the transmitting antenna it is observed that resonance cones, instead of being a single sharp peak, become spatially modulated by a multiperiod interference pattern; this interference pattern can dominate over the phasing imposed by a grill antenna. A simple theory shows that this effect occurs when ${\omega }_{\mathrm{pe}}\frac{\mathcal{r}}{c}\gg 1$ and that it is caused by electromagnetic terms neglected in the electrostatic approximation.

Measurements are reported which relate to the dissipation and superfluid density of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ flowing through a long rectangular channel of cross section 48 μm × 2.86 mm at currents between 5 × ${10}^{-2\mathrm{}}$ g ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ and 5 × ${10}^{-5\mathrm{}}$ g ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ and at temperatures down to $\frac{T}{T_c}=0.52\mathrm{}$. The results show a complex velocity dependence in both phases.

High-resolution photoemission spectra of the Si $2p$ level for freshly cleaved Si(111) reveal two additional core-level structures which are shifted relative to the bulk. The observed shifts are 0.59±0.04 eV to lower and 0.3±0.03 eV to higher binding energy, respectively. These shifted peaks, which vanish with increasing contamination of the surface, are shown to be directly correlated with reconstruction on the Si(111) 2×1 surface.

The force transmitted through the layers of smectic-$A$ and smectic-$B$ phases of butyloxy-benzylidene-octylanine (4O.8) have been measured at frequencies between 1 and 10 000 Hz, in the presence of an ac shear parallel to the layers. It is found that the smectic-$A$ behaves as a viscous fluid. The smectic-$B$ shows an elastic response, with a shear modulus $C_{44}\sim {10}^6$ cgs units. The low-frequency plastic behavior and the high-frequency dispersion which is related to internal friction are discussed.

The C-O stretching vibrational mode of the Cu(100) + $c(2\mathrm{}\times 2) \mathrm{CO}$ system has been examined by angle-dependent inelastic electron scattering. The mode is collective and its dispersion is found to be dominated by dipole-dipole interactions among the adsorbed molecules. The vibrational excitation cross section is satisfactorily described by dipole scattering theory.

Monte Carlo simulations and $\epsilon$ expansion techniques are used to analyze the behavior of antiferromagnetic Potts models and the Ashkin-Teller model. The Monte Carlo data show that the three- and four-state antiferromagnetic Potts models have an ordered low-temperature phase in three dimensions. Evidence is presented for the existence of a novel low-temperature, metastable, glassy "plastic crystal" phase in the four-state antiferromagnetic Potts model in three dimensions.

Theoretical values of the mutual-friction parameters $B$ and $B^{\prime }$ are derived from a purely hydrodynamic model, in close agreement with experimental data in the temperature range from 1.7 to 2.1 K.

The spatial and temporal characteristics of phonon pulses generated in the interband energy relaxation process of photoexcited $e-h$ pairs in GaAs and InP are reported. With use of a superconducting Pb tunnel junction as a phonon threshold detector, it is shown that the energy transport occurs via near-zone-edge transverse acoustic phonons and that over lengths of the order of several millimeters the pulse propagation shows all features of ballistic transport in a dispersive medium.

Reported here are polarocaloric (electrocaloric) measurements of a ceramic specimen of lead zirconate modified with ${\mathrm{Ti}}^{4+}$ and ${\mathrm{Sn}}^{4+}$. Temperature changes as large as 2.0 °K were recorded. The temperature change varies roughly as the square of the polarization change. The measured effect agrees with a thermodynamic calculation which utilizes the temperature dependence of polarization versus electric field.