The vector analyzing power ($i{T}_{11}$) in elastic $\pi -d_{\mathrm{pol}}$ scattering has been measured for several angles at $T_{\pi }=142\mathrm{} \mathrm{and} 256$ MeV. The results are compared with calculations reported in the literature. At the lower energies, Faddeev calculations agree fairly well with the data. At the higher energies, the experimental results differ markedly from any conventional calculation, but agree surprisingly well with predictions in which effects of dibaryon resonances are explicitly included.

For highly asymmetric electron-capture collisions, the ratio of the small charge $Z_P$, here taken to be that of the projectile, to the large charge of the target $Z_T$ forms the natural expansion parameter. Previous treatments with use of $\frac{Z_P}{Z_T}$ expansions obtain the impulse approximation which is shown to err by unknowingly neglecting terms of order ${\left(\frac{Z_T}{v}\right)}^2$; a simple correction factor in the limit of small $\frac{Z_P}{v}$ is derived.

The reflection of a light pulse from a spatially dispersive medium is investigated theoretically. For laser frequency at exciton resonance, spatial dispersion enhances the reflected transients associated with the light pulse. For the case of CdS and GaAs crystals, the transient intensities are about 10% of the incident intensity at a time 0.1 ps after the trailing edge of the reflected signal. The theory predicts a crossover from exponential to slow power-law decay rate of transient reflectivity; this occurs at a characteristic time ${\zeta }_c\sim 1$ ps after the trailing edge of the pulse for CdS and GaAs.

Experiments have been performed to measure the neutral pressure buildup behind the limiter as a function of plasma density and gas species. The results indicate that a passive mechanical limiter effectively removes from the vacuum vessel up to 20% of the atoms injected during a discharge. The feasibility of mechanical limiters removing the fusion-reaction helium ash, thus negating a major need for magnetic divertors, is discussed.

Large-amplitude, low-phase-velocity, axisymmetric electron cyclotron waves have been excited and propagated more than 10 wavelengths on an intense relativistic-electron beam transported along a magnetic field inside a cylindrical vacuum waveguide. Measurements of wavelength and azimuthal symmetry have been accomplished. Wave-phase-velocity control, essential for collective ion acceleration, has been demonstrated by spatially varying the magnetic field strength. From measured wave quantities, on-axis accelerating fields of 10 MV/m are inferred.

It is shown that two-dimensional solitons, being vortices propagating at characteristic speeds, can be formed in a long-wavelength drift-wave turbulence. A random set of vortex solitons scatters plasma particles and leads to enhanced diffusion, whose coefficient can become as large as that due to convective cells.

A novel method for creating the spheromak configuration has been proposed and verified experimentally. The scheme is based on a transfer of poloidal and toroidal magnetic fluxes into a plasma from a "flux core." We present the first experimental verification of this quasistatic (${\tau }_{\mathrm{Alfv}\acute{\mathrm{e}}\mathrm{n}}\ll {\tau }_{\mathrm{form}}<{\tau }_{\mathrm{diff}}$) formation scheme, which is suitable for future scaleup to fusion-reactor parameters.

Experiments are reported on velocity bunching of near-zone-edge phonon pulses generated in the interband energy-relaxation process of photoexcited electron-hole pairs in GaAs and InP. The bunching is achieved by scanning the photoexcited region along the direction of phonon propagation at various velocities corresponding to different dispersive points on the phonon branch. This intense, tunable phonon source can be operated in the 10-ÅA wavelength region.

Magnetic-resonance studies of the 1420-MHz transition in atomic hydrogen have yielded an accurate value for the binding energy of atomic H on liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. A value of 0.93±0.05 K is derived from two independent determinations of the surface binding: one from the shift in the hyperfine frequency, and the other from the recombination rate. The rate constant for H-H recombination in zero field and the hyperfine frequency of an H atom in the bound surface state have also been determined.

A temperature-dependent expression for the condensate fraction $n_0$ for He II based on a model Hamiltonian for superfluids is presented. This gives roughly the same magnitude for $n_0$ as is observed. The model also suggests the following behavior as $T\to 0$ for the roton effective mass ${\mu }_r\mathrm{}\left(T\right)={\mu }_r\mathrm{}\left(0\right)\mathrm{}[1-(\frac{m_{\mathrm{He}}}{24{\hslash }^3\mathrm{cn}}\left){\left(k_{\mathrm{B}}T\right)}^2\right]$ and the roton minimum energy $\Delta \mathrm{}\left(T\right)=\Delta \mathrm{}\left(0\right)\mathrm{}[1-(\frac{m_{\mathrm{He}}}{24{\hslash }^3\mathrm{cn}}\left){\left(k_{\mathrm{B}}T\right)}^2\right]$.

It is shown that a noninteracting—spin-wave theory, in which the central component observed by neutron scattering is attributed to scattering from spin-wave—density fluctuations, gives intensities comparable to, or greater than, the intensities predicted by the soliton theory, and provides a better fit to the variation of the intensity with field, temperature, and wave vector. It is concluded that further work is needed to distinguish the soliton contribution to the central-peak intensity from the scattering by pairs of spin waves.

The shallow-deep instability of substitutional donors and core excitons is discussed, with inclusion of all intervalley interactions. Shallow levels result in Si for a screened point-charge potential, because intervalley overlap and kinetic energy balance the potential-energy terms, which are severely reduced, at substitutional sites, by umklapp effects. Contrary to recent claims based on consideration of potential energy only, many-valley interactions cannot therefore be invoked to predict deep core-exciton levels in Si.

Observations of intermediate-energy proton capture populating unbound states are analyzed in terms of the bremsstrahlung emitted during single-particle transitions. The model accounts for the major features of the data. The present results suggest that these experiments can yield information on the structure of highly excited states.

The excitation energies and the ($p$,$n$) cross sections of the giant Gamow-Teller resonance as well as the isobaric analog state in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ are calculated. Similar to the results in electron scattering, the theoretical spin-flip strength overestimates the experimental one appreciably. The excitation energies of the spin-dependent excitations and the isobaric analog resonance can only be explained simultaneously if the effects of the "dynamical theory of collective states" and of the one-pion- and one-$\rho$—exchange potential are taken into account.

An electrostatic ion trap was used to trap ${\mathrm{Ne}}^{q+} (1\mathrm{}<~q<~10)$ ions created by a fast xenon beam passing through neon gas. Exponential decay in time of the ${\mathrm{Ne}}^{10+}$ fraction due to electron capture from neon gas was observed and the decay rates measured. For mean kinetic energies between 7-45 eV, the total electron-capture cross section (${\sigma }_{\mathrm{ec}}$) is found to be velocity independent. For this energy range we obtain ${\sigma }_{\mathrm{ec}}\left({\mathrm{Ne}}^{10+}\right)=2.4\mathrm{}\times {10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$, with an estimated uncertainty of 30%.

The first observation of pressure-induced extra resonant enhancements of a coherent four-wave—mixing signal is reported. When the difference between two input frequencies, ${\omega }_1$ and ${\omega }_2$, corresponds to the separation of two unpopulated upper levels, a resonant enhancement of the generated intensity at $2{\omega }_1-{\omega }_2$ is caused by collisions.

The steady-state solution of the nonlinear Vlasov-Poisson equations is reduced to a non-linear eigenvalue problem for the case of double-layer (potential-drop) boundary conditions. Solutions with no relative electron-ion drifts are found. The kinetic stability is discussed. Suggestions for creating these states in experiments and computer simulations are offered.

The shear mechanical properties of freely suspended films of a liquid crystal, $p$-butoxybenzylidene-$p^{\prime }$-octylaniline (BBOA or 40.8), have been measured in the smectic-$A$ and smectic-$B$ phases. All films showed solidlike response well above the bulk $A-B$ transition temperature. Both the in-plane shear modulus and shear dissipation exhibited a very strong frequency dependence in the $A$ and $B$ phases. Films which were two molecules thick showed anomalous behavior at much higher temperatures than thicker films.

The collective translational structure of dilute suspensions (∼ 0.1% by weight) of charged, spherical, and colloidal particles under shear is investigated by light scattering. When subjected to increasing shear rate, the equilibrium bcc Wigner lattice exhibits two major, reversible, disordering transitions. Transition II occurs at low shear, is kink mediated and results in freely slipping two-dimensional hcp layers. At higher rates, transition I occurs where these two-dimensional layers melt via shear-induced fluctuations (phonons) to produce an amorphous structure. The amorphous structure has stringlike particle correlations which ultimately disappear.

A propagating magnetic texture has been observed in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ confined to 17-μm slabs with use of pulsed NMR. The results support a model of an expanding lattice of solitons in the order parameter. The propagation velocity approaches the spin-wave velocity as $T\to T_c$, and goes to zero for $T<\mathrm{}0.86\mathrm{}{T}_c$. Despite the narrow geometry, the solitons observed involve distortions of both the spin and orbital degrees of freedom.