A new method for the study of time reversal violation is described. It consists of measurements of the forward-backward asymmetry in individual gamma-ray transitions resulting from unpolarized neutron capture in p-wave resonances. An experiment with a ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ target performed at the Dubna pulsed neutron source has been analyzed and a limit on the time reversal odd, parity even interaction extracted. The possibility of experiments using the powerful pulsed neutron source at Los Alamos are considered.

A new probe of dynamical effects in heavy-ion induced fission is proposed. This is the ‘‘long-lifetime’’ tail of the time distribution of fission events, or the so-called long-lifetime fission component (LLFC). The excess of LLFC over its standard statistical-model value is calculated by taking into account dissipation and fluctuations of the collective nuclear motion. The magnitude of this excess is shown to be much larger and its dependence upon the reduced friction parameter to be much stronger than those of the corresponding excess of the pre-scission neutron multiplicity which is at present a commonly used probe of dynamical effects in heavy-ion induced fission. Experiments for measuring LLFC are proposed which can provide decisive information about the strength of nuclear friction for compact configurations in nuclear fission.

Multifragment azimuthal correlation functions have been measured as a function of beam energy and impact parameter for the Ar+Sc system (E/A=35 to 115 MeV). The observed azimuthal correlation functions—which do not require corrections for dispersion of the reaction plane—exhibit strong asymmetries which are dependent on impact parameter and beam energy. Rotational collective motion and flow seem to dominate the correlation functions at low beam energies. It is proposed that multifragment azimuthal correlation functions can provide a useful probe for intermediate energy heavy ion reaction dynamics.

We study various nonequilibrium properties of a mixture comprised of pions, kaons, and nucleons. Quantitative calculations of the relaxation/collision times, the degradation of momentum in elastic collisions, and the relaxation times of shear and heat flows, drag flow, and diffusion flow are performed. Binary interactions are specified through the empirical phase shifts. The heavier kaons and nucleons are found to equilibrate more slowly than pions. These results shed new light on the influence of collective flow effects on the transverse momentum distributions of kaons and nucleons versus those of pions in ultrarelativistic nuclear collisions.

We report a new experimental situation where the main contribution to the energy of electrons submitted to an ultrastrong laser field is given by the ponderomotive force. Electrons released from a low-density gas medium with energies up to 5 keV have been detected, which is far above the energy acquired during the ionization process. Numerical simulations of the electron trajectories are in good agreement with the experimental results.

We have ionized Rydberg atoms using subpicosecond half-cycle electromagnetic pulses. The threshold electric field required to ionize a Rydberg state with effective quantum number ${\mathit{n}}^{\mathrm{*}}$ is found to scale as ${\mathit{n}}^{\mathrm{*}\mathrm{-}2}$ for states with ${\mathit{n}}^{\mathrm{*}}$>13 in contradistinction to the ${\mathit{n}}^{\mathrm{*}\mathrm{-}4}$ threshold scaling for static field ionization and high order multiphoton ionization. This novel result is explained using a classical model.

We report the first measurements and associated theory for angular correlations of sequential cascading photons for an atomic system in which a scattering plane is defined. The cascade radiation from the n=3 levels of atomic hydrogen excited by 290 eV electrons is observed. The first determinations of a rank-4 multipole and of the magnetic sublevels of the 3d state have been made. The measured angular correlations and the deduced multipole moments have order-of-magnitude agreement with Glauber, Born, and six-state close-coupling model predictions.

We have measured probability distributions of quadrature-field amplitude for both vacuum and quadrature-squeezed states of a mode of the electromagnetic field. From these measurements we demonstrate the technique of optical homodyne tomography to determine the Wigner distribution and the density matrix of the mode. This provides a complete quantum mechanical characterization of the measured mode.

Using numerical methods we find that anti-Stokes generation in stimulated Raman scattering can cause Raman solitons to decay, unless the fields are phase matched. Photon number conservation then leads to unusually high intensities in regions where both the Stokes and anti-Stokes fields vanish. For large propagation lengths, the pump soliton can decay considerably, and as a result, the fields do not interact strongly. We therefore predict the formation of solitonlike pulses at the anti-Stokes frequency.

We show that the power emitted from phase-locked soliton oscillators can exceed the upper limit given by the theory for superradiance from phase-locked point oscillators. As an experimentally relevant example, we consider two magnetically coupled long Josephson junctions, operated in single-fluxon modes. Analytical results indicate that the coupling between the two oscillators enables the phase-locked modes to localize in space thereby creating the possibility of an enhancement of the power level beyond the point-oscillator limit. Good agreement is found between analytical results and numerical simulations, and with recently published experimental data.

We propose a model system based on the Euler equations with integral constraints to describe high-Reynolds-number Navier-Stokes turbulence. This system is Galilean invariant. It is demonstrated computationally that the system, under appropriate constraints, evolves to a quasiequilibrium state which reproduces accurately both low- and high-order statistical measures of turbulence observed in laboratory experiments and direct numerical simulations. A large-eddy simulation model based on the constrained Euler system is formulated and computationally validated. The theoretical interest of the proposed system in the context of nonequilibrium statistical mechanics is briefly discussed.

Electron trajectories diverge exponentially in a sufficiently small-scale electrostatic field with a static external magnetic field. This electron trajectory instability results in the electron heating in field structure typical for the collisionless shock front ramp. The magnitude of the effect is sufficient to explain the observed heating at the Earth’s bow shock and interplanetary shocks. The heating features are consistent with the observations.

Time-resolved x-ray spectroscopy is used to study the implosion of indirectly driven inertial confinement fusion capsules on the Nova laser. Through the use of Ar dopant in the fuel, measurements of the peak temperature, from emission line ratios, and density, from line broadening, are obtained. These measurements indicate peak electron temperatures of ∼1–1.6 keV and electron and deuteron densities in the range of (1.0–2.0)×${10}^{24}$ ${\mathrm{cm}}^{\mathrm{-}3}$, depending on the type of laser drive used. These ion densities, which approach those of stellar interiors, are the highest inferred by direct analysis of Stark-braodened line profiles.

Molecular-resolution atomic force microscope images of Ba arachidate Langmuir-Blodgett multilayers show two previously unknown structures, a tilted (26°) triclinic packing with a 3×1 sawtooth height modulation, and a tilted (19°) rectangular herringbone packing with an alternating vertical offset, along with untilted disordered regions, all within the same molecular layer. The submicron extent of each region, the extent of twinning and defects, and the complexity of the molecular packing make the determination of the lattice structure of these materials impossible by any other technique.

The small magnitude of (${\mathit{T}}_{\mathit{c}}$-${\mathit{T}}^{\mathrm{*}}$)/${\mathit{T}}_{\mathit{c}}$, where ${\mathit{T}}_{\mathit{c}}$ is the nematic-isotropic phase transition temperature and ${\mathit{T}}^{\mathrm{*}}$ denotes the virtual transition temperature, has been a long-standing puzzle in the physics of liquid crystals. We show that by extending the mean field theory to include the isotropic, density-dependent component of the molecular interaction the magnitudes of both (${\mathit{T}}_{\mathit{c}}$-${\mathit{T}}^{\mathrm{*}}$)/${\mathit{T}}_{\mathit{c}}$ and the density change at the transition automatically become in accord with the experimental values. In addition, the theory yields a value of ${\mathit{dT}}_{\mathit{c}}$/dp, where p denotes pressure, that is on the same order as the experiment.

Neutron-diffraction and light-scattering studies have been performed on a network glass subject to structural modifications. Large changes of the first sharp diffraction peak (FSDP) and the low frequency dynamics (the boson peak) are demonstrated by gradually changing the intermediate-range structural ordering, the short-range order being preserved. A recently suggested ‘‘universal’’ correlation for glasses between the positions of the FSDP and the boson peak is shown to fail; in fact opposite trends are observed.

We report on a new technique, Auger electron spectroscopy induced by impact of specularly reflected energetic protons. The Cu ${\mathit{M}}_{2,3}$VV Auger signal induced by 175 keV protons incident on clean and Ag-covered Cu(111) is measured. At 0.5° incidence angle, a coverage of 1 monolayer produces a reduction in Auger signal to merely 2% of the clean-surface signal. This is far less than for electron or large-angle proton excitation (37%). The extreme reduction is due to the fact that the grazingly incident protons are specularly reflected and solely create core holes at top surface layer atoms.

We have investigated the various phase boundaries in the (x,T) phase diagram of the solid solution ${\mathrm{Rb}}_{1\mathrm{-}\mathit{x}}$(${\mathrm{ND}}_4$${)}_{\mathit{x}}$${\mathrm{D}}_2$${\mathrm{PO}}_4$ by means of the nonlocal NMR probe ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$. Clear evidence for soft-mode behavior was found for the phase transitions to the long-range-ordered ferroelectric (x=0.15) and antiferroelectric (x=0.95) phases, whereas, thermally activated behavior was observed for the deuteron glass composition x=0.50. However, the composition x=0.70 exhibits a diffuse phase transition to ‘‘long-range’’ antiferroelectric order and a ‘‘relaxor’’ type dynamics.

We study the growth of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films on weakly attractive substrates. Close to the substrate the film grows by formation of well defined liquid layers. Above a minimum stable coverage, a liquid monolayer uniformly covers the surface. Upon increasing the coverage a second liquid layer begins to grow by the formation of two-dimensional liquid ‘‘clusters.’’ Above a certain coverage, the second layer leaves vacuum-cluster coexistence, and the system regains the full planar symmetry. The scenario is repeated for a third liquid layer. The results are interpreted in terms of recent experiments of helium on graphite.

We have studied the high-order commensurate phase of the clean Mo(001) surface at about 100 K with surface x-ray diffraction. Our quantitative structure analysis demonstrates the relevance of the periodic lattice distortion model, but the detailed displacement pattern is closer to a square wave than a sine wave. This probably arises from specific bonding, similar to that seen in W(001).