It is shown that the curl of the velocity field generally identified with ${\overrightarrow{\mathrm{v}}}_s$ in the $A$ phase of superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is entirely determined in the absence of singularities by the spatial gradients of the order-parameter symmetry axis $\overrightarrow{\mathrm{l}}$. As a simple application of this relation it is argued that in a texture of cylindrical symmetry in a volume $V$, the liquid should have a nonvanishing thermal-equilibrium orbital angular momentum of order ${\rho }_s\frac{V\hslash }{M}$.

A relativistic low-energy electron-diffraction theory has been modified to allow computations for energies up to 200 eV. Its application to W(001) yields intensity profiles in reasonable correspondence with experiment, and pronounced polarization profiles which show encouraging agreement with novel and as yet limited experimental data. A high sensitivity of the polarization profiles to displacement of the topmost layer suggests that spin polarization measurements could be valuable for structure determination of surfaces involving heavy atoms.

We report a crystal-electric-field effect on the low-temperature thermal expansion of TmSb, manifesting itself as a Schottky-type anomaly. From our results we deduce a volume dependence of the crystal-field level splitting which is in contradiction to point-charge-model expectations.

The electron-coupled phonon spectrum ${\alpha }^{2}F$, $\lambda$, and ${\mu }^{*}$ have been determined for polycrystalline and high-purity, single-crystal niobium from tunnel junctions fabricated with three different counterelectrodes. All spectra compare well with phonon spectra extracted from neutron-scattering experiments. Values of $\lambda$ are BCS-like and ${\mu }^{*}$ is always negative. Computer-modeling studies describing a niobiumlike material cannot generate an acceptable set of strong-coupling parameters.

We show that parallel static and rf magnetic fields applied in the basal plane of single-crystal gadolinium samples excite phonons having a frequency equal to that of the rf field. These results, including measurements of the phonon signal as a function of angle between the rf and dc fields and as a function of the power input to the cavity, are shown to be inconsistent with current magnetoelastic theory.

The angular distribution of ions desorbing from the surface of a solid is studied theoretically. Specific calculations for oxygen adsorbed on the (100) face of tungsten are presented. The angular patterns result from the three-dimensional spatial variations in the ion-solid potential surface. Details of the pattern are found to vary sensitively with changes in the surface geometry.

Field-induced magnetization densities of Sc metal determined from augmented plane-wave functions, including local density-of-states effects, were found to show a large spatial expansion of the $3d$ density and strong bonding effects. These result in an "anomalous" behavior of the neutron magnetic form factor which has been found in the experiments of Koehler and Moon.

The magnetic form factor of metallic scandium has been measured at a temperature of 100 K in an applied field of 57.2 kOe by the polarized-neutron technique. Contrary to results on other $3d$ metals, the form factor is significantly different from that for the $3d$ electron in the free atom. Our results agree rather well with those of a calculation by Gupta and Freeman based on APW wave functions.

The effective-mass equation for indirect excitons in Ge is solved taking the degeneracy and anisotropy of the bands into account. The calculated binding energies of the anisotropy split ground state (4.18 and 3.17 meV) are in excellent agreement with experiment (4.15 and 3.14 meV). The method is then extended to calculate the energy-momentum dispersion of excitons, which are strongly nonparabolic, and account well, with no adjustable parameters, for the recently measured modulated absorption line shape.

Intense tuneable synchrotron radiation was used to perform a high-resolution study of the resonant scattering response of Cu metal in the x-ray regime. One finds in the transition regime from fluorescence to resonant scattering that the linewidth of the emitted radiation becomes narrower than the lifetime-limited width of the fluorescent radiation.

The differential cross section for $n-p$ elastic scattering in the angular region $145°<{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<180\mathrm{}°$ has been measured with high statistical accuracy using the monoenergetic neutron beam at Clinton P. Anderson Meson Physics Facility. The results differ significantly from previous Dubna and Princeton-Pennsylvania Accelerator results but agree reasonably well with recent Saclay data except at extreme backward angles.

The spectrum of charmonium in the presence of a charmed-meson continuum is investigated. Radiative rates are in considerably better agreement with data than for the naive model, the largest discrepancy being a factor 2-3 for ${\psi }^{\prime }\to \gamma +{}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$. The model accounts for the peak at ∼ 4.2 GeV in $\sigma (e\overline{e}\to \mathrm{had})$, and predicts a further peak at ∼ 3.75 GeV due to $1{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$. The latter would be the most favorable location for a charm search in $e\overline{e}$ collisions.

We present preliminary results from an investigation of the reaction $n+p\to \left(p{\pi }^{-}\right)+p$ for neutron momenta in the range of 50 to 300 GeV/c. The data display a strong correlation between the mass of the $p{\pi }^{-}$ system and the four-momentum transferred in the production. Cross sections for producing low-mass ($p{\pi }^{-}$) systems are independent of energy to within 10% accuracy.

We have examined the decay angular distributions of ($p{\pi }^{-}$) systems produced in the reaction $n+p\to \left(p{\pi }^{-}\right)+p$ for neutron momenta between 50 and 300 GeV/c. The production process appears to be dominated by comparable contributions from both the pion-exchange Deck mechanism and the proton-exchange Deck mechanism.

The pion-exchange contributions to the two-photon amplitude are derived and gauge invariance of the complete amplitude is shown. A low-energy theorem for a general two-photon process is derived and the pionic contribution to the magnetic susceptibility is calculated. The contribution of this quantity to $n-p$ two-photon radiative capture is shown to be small.

The charge, kinetic energy, and angular distributions of reaction products formed during bombardment of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ with 1130-MeV ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ ions have been studied in detail. The measured total direct-reaction cross section of 2840±150 mb is in good agreement with the total reaction cross section obtained by analysis of the elastic-scattering distributions. The principal reaction channel is observed to be due to the strongly damped collision mechanism.

The heavy-ion motion in sub-Coulomb collisions generates extreme magnetic fields. The hyperfine splitting of the spin-½ quasimolecular electronic states in U + U is found to reach 10% of the molecular binding energy (100 keV). Also Pb+Pb and Xe+Xe collisions are considered.

It is suggested that, in a tokamak discharge, the initial rapid current penetration and the disruptive instability may each be attributed to a type of nonlinear double-tearing instability which causes growth and overlap of radially separated magnetic islands. The ensuing reconnection and braiding of magnetic lines would enhance local radial heat and particle transport and could permit rapid redistribution of plasma current, inducing positive or negative spikes in the loop-voltage signal.

Plasmon dispersion and anisotropy in the metallic polymer ${\left(\mathrm{SN}\right)}_x$ were investigated directly by electron-energy-loss spectroscopy. A positive dispersion relation was observed for plasmons propagating along the polymer-chain $b$ axis. As the plasmon wave vector changes from parallel to perpendicular to the $b$ axis, the plasmon energy decreases from 2.5 to 1.5 eV consistent with the view that ${\left(\mathrm{SN}\right)}_x$ is a poor conductor in the perpendicular direction rather than a quasi-one-dimensional metal.

Metastable relaxed excitons created by pulsed electron irradiation in alkali-halide crystals are excited to higher states by a laser pulse. Consequent changes in excitonic absorption and emission yield data on triplet-singlet conversion and on polarization of the optical transitions. It is found that $F$ centers are formed upon promotion of self-trapped excitons from the lowest metastable level to the second excited level in KCl.