Mode-selective excitation of Alfvén waves is made by use of azimuthally rotating, radio-frequency antennas in the central cell of the GAMMA 10 tandem mirror. It is found that the wave polarization reverses from right handed in the central cell to left handed in the anchor cell and vice versa. Ions in the anchor cell are significantly heated by a fast wave excited in the central cell and not by a slow wave. The polarization reversal and the wave-mode-dependent ion heating are interpreted in terms of a linear mode conversion which is caused by a mode coupling between fast and slow Alfvén waves via a spatial modulation of the magnetic field in the quadrupole-field region.

The magnetization and the ac susceptibility of hcp solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ have been measured for molar volumes V from 18.34 to 19.29 ${\mathrm{cm}}^3$/mole at temperatures down to 38 μK. The Weiss temperature obtained from the magnetization is proportional to ${\mathit{V}}^{18.4\pm 0.6}$. The Zeeman-exchange relaxation time obtained from the ac susceptibility indicates the appearance of the critical phenomenon for the sample with 19.29 ${\mathrm{cm}}^3$/mole.

Novel local free-energy functionals are presented, generalizing the de Gennes-Fisher critical-point ansatz, for obtaining fluid interface tensions near critical end points and critical wall tensions. Nonclassical exponents, proper analyticity in T, etc., are embodied. New ‘‘interpolated linear-model’’ and ‘‘trigonometric’’ parametric equations of state then lead to universal ratio estimates ${\mathit{K}}_{+}$/${\mathit{K}}_{\mathrm{-}}$≃-0.83, (${\mathit{K}}_{+}$+${\mathit{K}}_{\mathrm{-}}$)/K≃0.$1_2$, for the amplitudes K of the critical and ${\mathit{K}}_{\pm }$ of the noncritical wall tensions.

Two 3D periodic structures are introduced based on so-called T polyhedrons. These structures can be used as mathematical models to describe the VNi alloys system in order to explain the twelvefold rotational symmetry in electron-diffraction patterns of VNi alloys. The 3D atomic models of the VNi alloy are first presented in this paper.

Using computer simulations, the power-law behavior of the interface growth of a spreading fluid is studied in a two-dimensional lattice model. The interface width exponent ν and the dynamical exponent k for the evolution of the front are consistent with their dynamical scaling relation. The magnitude of these exponents seems to depend upon the nature of the substrate and the concentration of the carriers of the wetting fluid.

Surface extended x-ray-absorption fine structure (SEXAFS) has been combined with scanning tunneling microscopy (STM) to determine both the local and long-range bonding properties of the Si(001)2×1-Sb interface. Sb ${\mathit{L}}_3$ edge SEXAFS shows that Sb dimers occupy a modified bridge site on the Si(001) surface with a Sb-Sb near-neighbor distance of 2.88±0.03 Å. Each Sb atom of the dimer is bonded to two Si atoms with a Sb-Si bond length of 2.63±0.04 Å. STM resolves the dimer structure and provides the long-range periodicity of the surface. Low-energy-electron diffraction of vicinal Si(001) shows that the Sb dimer chains run perpendicular to the original Si dimer chains.

Fourier-transform infrared spectroscopy on the charge-state-dependent local modes of the off-center substitutional oxygen impurity in GaAs has revealed an inverted ordering of the two gap levels. The metastable one-electron state shows the characteristic disproportionation into the zero- and the two-electron state. From the thermally activated decay of the local mode lines and the observed threshold energies for the photoionization cross sections ${\mathrm{\sigma }}_{\mathit{p}}^0$(1) and ${\mathrm{\sigma }}_{\mathit{n}}^0$(2), binding energies of 0.15 and 0.62 eV for the first and the second electron, respectively, are deduced.

We report the observation of an exciton redshift with a below-gap laser beam, linked to the presence of a bound two-pair state in CuCl. This change in the shift direction for the optical Stark effect in semiconductors relies upon the predominant creation of virtual biexcitons, as shown by the polarization selection rules. Our experiment demonstrates the importance of the biexciton in the description of the optical Stark effect.

The dynamics of intervalley scattering of electrons is investigated in GaAs with 6 fs optical pulses at room temperature. We report the observation of a ‘‘resonant coupling’’ between the Γ and X conduction bands. This effect slows the apparent rate of scattering of carriers in the Γ valley at energies near the minimum of the X valley.

The effect of light-induced drift of quantum-confined electrons in semiconductor heterostructures is predicted. The effect manifests itself as the electric current in the heterostructure plane in response to optical excitation with the frequency close, but not exactly equal, to a transition frequency between levels in the heterostructure. The current reverses its direction with a change in the detuning sign, and vanishes if the radiation polarization is normal to the heterostructure plane.

We show that very accurate ground-state energies and correlation functions can be obtained from an approximate, variational form of the widely used auxiliary-field simulation method. It is derived by recasting this method as a diffusion problem, and does not exhibit the poor statistical behavior due to vanishing normalization or ‘‘sign’’ common to exact fermion simulations. We give illustrative results for two-dimensional Hubbard models.

Transport in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ was studied by modulating the resistance and superconductive kinetic inductance via capacitively charging (001) surfaces. The mobility varies inversely with temperature, the effective mass is 5(±1)${\mathit{m}}_{\mathit{e}}$ at low tmeperature, and hole carrier densities are temperature independent and nearly the same in normal and superconducting states. Transition temperatures at ideal surfaces are equal to the bulk and show notably weak modulation with carrier density.

We present femtosecond time-resolved measurements on the high-${\mathit{T}}_{\mathit{c}}$ superconductor ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10}$. At temperatures below ${\mathit{T}}_{\mathit{c}}$, we observe a relaxation process which is distinct from the equilibration of hot carriers in the normal state. Our results demonstrate an increasing relaxation rate as the superconducting gap opens. This is consistent with the behavior of conventional metallic superconductors.

Disordered two-dimensional soap froth has been simulated, with a gas fraction φ less than unity. Upon decreasing φ, it is found that the system loses its rigidity at ${\mathrm{\phi }}_{\mathit{c}}$=0.84. This value is identified with the dense random packing of hard disks. Results are presented for the variation of yield stress and shear modulus, the latter being tentatively related to elastic-network theory.

We show that isochoric differential x-ray experiments of Bosio, Chen, and Teixeira are consistent with the possibility that water molecules can exist in distinct configurations characterized by either four or five neighbors in the first coordination shell. Associated with the molecules with five neighbors are defects in the tetrahedral bond network (‘‘bifurcated bonds’’) which offer paths with low energy barriers between different network configurations and in turn enable the fast restructuring of the network with thermal energies kT much smaller than the hydrogen-bond energy.

We have achieved control of chaos in a physical system using the method of Ott, Grebogi, and Yorke [Phys. Rev. Lett. 64, 1196 (1990)]. The method requires only small time-dependent perturbations of a single-system parameter and does not require that one have model equations for the dynamics. We demonstrate the power of the method by controlling a chaotic system around unstable periodic orbits of order 1 and 2, switching between them at will.

A method is developed which uses the exponential sensitivity of a chaotic system to tiny perturbations to direct the system to a desired accessible state in a short time. This is done by applying a small, judiciously chosen, perturbation to an available system parameter. An expression for the time required to reach an accessible state by applying such a perturbation is derived and confirmed by numerical experiment. The method introduced is shown to be effective even in the presence of small-amplitude noise or small modeling errors.

The oscillations of a linear triatomic molecule with the first atom driven at a constant velocity v are studied numerically. As v increases, we observe a sequence of transitions from quasiperiodicity to chaos, mode locking, chaos, another mode locking, then to chaos before the atoms break off. The largest Lyapunov exponent does not rise linearly with the driven velocity. The mode-locking structure for the last onset to chaos has a universal fractal dimension 0.871±0.001 at a winding number far from the golden mean.

A model for dense packings of disks rolling on each other is presented. This model might have application for turbulence, tectonic motion, and mechanical gearworks. A full classification of solutions with fourfold loops is given. The fractal dimensions are calculated and compare favorably with Kolmogoroff scaling of turbulence.

The (2+1)-dimensional Davey-Stewartson I system is quantized, and the exact eigenvalues and eigenfunctions of the Hamiltonian are obtained. Thermodynamic quantities are also given. Although it is quantized by using the commutation relations for bosons, the energy spectrum and thus the thermodynamic quantities reveal the characteristics of a system with two species of independent fermions.