Photoelectron spectra in xenon are obtained for (6+1)-photon ionization with intense laser pulses (λ=594 nm, I=5×${10}^{13}$ W/${\mathrm{cm}}^2$). By comparing spectra obtained with 300-fs and 600-fs pulses it is shown that the ground state is depleted by nondiabatic passage through high lying Rydberg states (nf) during the rise of the pulse. Spectra are well reproduced by a simple theory including both six-photon excitation to the Rydberg states and one-photon ionization out of these states.

A pair of closely lying states of opposite parity and the same total electronic angular momentum J=10 at 19 797.96 ${\mathrm{cm}}^{\mathrm{-}1}$ in dysprosium are experimentally investigated with the goal of evaluating parameters relevant to P and P,T violation experiments. Measurements of lifetimes, electric polarizability, and energy intervals between isotope and hyperfine components are presented.

Minimum energy structures for large carbon cages are investigated using realistic atomic potentials. Above a critical size of ∼6000 there is a stability crossover from single to multilayer cages. The lowest energy atomic configuration of a cage of any size consists only of hexagons and pentagons and is polyhedral in shape. Lowest energy defects involve either rearrangements between pentagons and hexagons or 5-7-5 triplets. Simulated transmission electron microscopy images show that a polyhedral onion appears spheroidal when viewed along its highest symmetry axis, and polyhedral when viewed from a more general direction.

We report on the coherent dynamics of excitonic wave packets observed in transient four-wave mixing experiments on strained InGaAs/GaAs quantum-well structures. The excitonic noneigenstates are created by using laser pulses shorter than the electron round trip time within the exciton orbital. A characteristic temporal modulation of the diffracted signal is observed, which resembles the coherent dynamics of an electron wave packet in a hydrogen atom expected for the case of a simultaneous excitation of all bound and the lowest continuum states.

The use of chaos to transmit information is described. Chaotic dynamical systems, such as electrical oscillators with very simple structures, naturally produce complex wave forms. We show that the symbolic dynamics of a chaotic oscillator can be made to follow a desired symbol sequence by using small perturbations, thus allowing us to encode a message in the wave form. We illustrate this using a simple numerical electrical oscillator model.

Helicity production in a homogeneous fluid is numerically demonstrated by using steady and unsteady forced Navier-Stokes equations: Even if all Fourier components of the force do not have helicity, nonlinear interactions of the zero-helicity components can generate helicity in the flow. When the Reynolds number increases, the flow nature changes from steady to temporally periodic to chaotic. The produced helicity has the largest time-averaged value in the periodic motion.

We report the first positive experimental observation of the optical activity effect on normal reflection. The experiment was performed along the optic axis in a gyrotropic semiconductor crystal of α-HgS, cinnabar, in a spectral region of strong absorption. Reflected light polarization azimuth rotation resulting from the reflection is in the order of ${10}^{\mathrm{-}4}$ rad and has pronounced dependence on ħω-${\mathit{E}}_{\mathit{g}}$.

Topological reconfigurations of the boundaries of thin fluid layers in Hele-Shaw flow are studied. A systematic treatment of the dynamics of the bounding interfaces is developed through an expansion in the aspect ratio of the layer, yielding nonlinear partial differential equations for the local thickness. For both density-stratified fluid layers and gravity-driven jets, numerical study of the dynamics at second order suggests strrongly the collision of the interfaces in finite time. There are associated singularities both in the fluid velocity and in geometric properties of the interfaces.

Viscous fingering in a linear channel is investigated in the presence of anisotropy, when the directions of easy growth are at 45° to the direction of the cell axis. Experimentally, when the velocity is increased, the stable fingers and the averaged unstable ones tend to occupy an increasing fraction of the cell width, in contrast with the standard situation. The numerical simulation and the analytical investigation reveal the existence of a new solution for the Saffman-Taylor finger which does not belong to the standard manifold.

Navier-Stokes turbulence at low Reynolds number (${\mathit{scrR}}_{\lambda }$≊15) is studied by high-resolution computer simulation. The energy spectrum in the range 5${\mathit{k}}_{\mathit{d}}$<k<10${\mathit{k}}_{\mathit{d}}$ is well fitted by ${\mathit{k}}^{\mathrm{\alpha }}$exp(-ck/${\mathit{k}}_{\mathit{d}}$), where ${\mathit{k}}_{\mathit{d}}$ is the Kolmogorov dissipation wave number, α≊3.3 and c≊7.1. High-order spatial derivatives of the velocity field exhibit strong intermittency, associated with gentle spatial variation of large-scale structure rather than with sparse, intense small-scale structures. Analysis by the direct-interaction approximation, which ignores intermittency, gives α=3, c≊11.

It is shown that in nonlinear discrete systems localized modes may exist in the form of self-induced gap solitons. Such structures appear due to a nonlinearity-induced gap in the cw spectrum, when one group of particles in the lattice plays a role of an effective periodic potential to other particles supporting a spatially localized oscillation. Two examples are considered and exact soliton solutions describing this type of localized modes are presented.

The effects of large-angle scattering, important for plasmas for which the Coulomb logarithm is of order 1, have been properly treated in calculating the range (R) and the ρR (the fuel-areal density) of inertial confinement fusion plasmas. This new calculation, which also includes the important effects of plasma ion stopping, collective plasma oscillations, and quantum effects, leads to an accurate estimate, not just an upper limit of ρR. For example, 3.5 MeV α’s from D-T fusion reactions are found to directly deposit ≃47% of their energy into 20 keV deuterons and tritons. Consequently the α range (R) and ρR are reduced by about 60% from the case of pure electron stopping.

A Fokker-Planck equation has been generalized to treat large-angle as well as small-angle binary collisions in plasmas. For moderately coupled plasmas [2≲ Coulomb logarithm (ln${\mathrm{\Lambda }}_{\mathit{b}}$)≲10], calculations have been made of the relaxation rates and transport coefficients. In general they differ from the standard (Braginskii) results by terms of order 1/ln${\mathrm{\Lambda }}_{\mathit{b}}$. Using a modified collision operator, a new vector potential that has a direct and practical connection to the Rosenbluth potentials is obtained. In addition, we calculate a reduced electron-ion collision operator that, for the first time, manifests the 1/ln${\mathrm{\Lambda }}_{\mathit{b}}$ corrections.

A covariant gyrokinetic fluctuation-dissipation theorem is used to predict unusual thermal-equilibrium fluctuation spectra for weakly electromagnetic gyrokinetic plasma in the limit of weak coupling. Wave number spectra are derived both by exact integrations of the frequency spectra and by resonance integrations over weakly damped normal modes. The former reduce in the electrostatic limit to previous heuristic results and are interpreted in terms of the concept of a ‘‘gyrokinetic vacuum.’’ The latter are interpreted in terms of a new form for the gyrokinetic energy conservation law and a new formula for the gyrokinetic plasmon action density.

The mechanism of different discharge modes, self-oscillations, and the period-doubling route to chaos is studied by comparing experimental results from a filament cathode discharge with particle-in-cell simulations. The self-oscillation process invokes ion trapping by charge exchange, double layer formation, and ion depletion. The exhausting of resources which underlies the period-doubling route is identified with incomplete ion refilling.

The physical mechanism for the generation of very high ‘‘dc’’ magnetic fields in the interaction of ultraintense short laser pulse with an overdense plasma target originates in the spatial gradients and nonstationary character of the ponderomotive force. A set of model equations to determine the evolution of the ‘‘dc’’ fields is derived and it is shown that the ‘‘dc’’ magnetic field is of the same order of magnitude as the high frequency laser magnetic field.

Intensity anomalies have been observed in the mass spectra of (${\mathrm{C}}_{60}$${)}_{\mathit{n}}^{+}$ and (${\mathrm{C}}_{70}$${)}_{\mathit{n}}^{+}$ clusters for n=13, 19, 23, 35, 39, 43, 46, 49, and 55. These numbers indicate that the closed shell clusters n=13 and 55 are probably icosahedra. The molecules in an incomplete shell seem to undergo a structural transition as the shell fills, similar but not identical to the transition proposed for Ar cluster ions.

A supercritical nucleus with isotropic surface tension growing in a diffusion field is found to evolve into a fractal structure at long times and small driving forces. A newly developed numerical method using a rotated-lattice sandwhich handles the anisotropy problem of the moving boundary. Scaling relations are found in agreement with a recently formulated theory.

We investigate the conductivity using Green’s functions in the Tomonaga-Luttinger liquid. It is shown that the resistivity has a linear temperature dependence if we take account of the physical process that the accelerated electron decays into spinon and holon. The effect of impurity scattering becomes visible only below a crossover temperature which strongly depends on the impurity strength, energy cutoff, and spin and charge velocities. The optical conductivity is also studied and it is shown that the relaxation rate has a linear frequency dependence.

We have made a detailed pressure–magnetic-field–temperature phase diagram study of the organic conductors (TMTSF${)}_2$${\mathrm{PF}}_6$ and (TMTSF${)}_2$${\mathrm{ClO}}_4$ in the low temperature regions dominated by the cascade of field-induced spin density wave (FISDW) transitions. The ${\mathrm{PF}}_6$ salt shows general agreement with the ‘‘standard model’’ for the FISDW and the pressure dependence of its high field insulating state connects nicely with the n=0 SDW. The ${\mathrm{ClO}}_4$ salt shows agreement with the standard model only when an anion ordering transition has been suppressed above ∼5 kbar.