Broad-band squeezed states of light are generated by forward nondegenerate four-wave mixing in a single-mode optical fiber cooled below 4.2 K. The minimum total noise level was (12.5 ± 0.5)% below the standard quantum limit.

Two-dimensional fluid flow past a circular obstacle has been simulated at the microscopic level by means of a molecular-dynamics approach. At sufficiently large Reynolds number the flow field is observed to exhibit characteristics common to real fluids, namely the appearance of eddies, periodic eddy separation, and an oscillatory wake. Very large systems—typically 160 000 particles—are required in order to provide adequate space for these flow patterns to develop.

We have measured the electric field in the high-voltage gap of a magnetically insulated intense-ion-beam diode by observation of the Stark shift of line emission from ions accelerating in the gap. The electric field distribution as a function of distance from the anode plasma has been compared with a theoretical model and is not consistent with a well confined electron sheath near the cathode. Furthermore, a very rapid gap closure at early time in the pulse was clearly observed.

It is shown through numerical simulation that the Rayleigh-Taylor growth rate for targets accelerated by laser ablation, is reduced below the classical value, ${\mathrm{}\left(\mathrm{kg}\right)\mathrm{}}^{\frac{1}{2}}$, by factors of 3-4 with 0.25-μm laser light. The simulation results are supported by an analytical expression for the growth rates. These results provide further evidence for the viability of high-aspect-ratio shells in direct-drive laser fusion.

Highly peaked carbon and molybdenum profiles occurred after hydrogen pellet injection. 40 ms after injection, carbon was well fitted by ${\left[\frac{T_e}{T_e\mathrm{}\left(0\right)\mathrm{}}\right]}^{1.5Z_{\mathrm{C}}}$ for $r\lesssim 6.5$ cm ($Z_{\mathrm{C}}=6\mathrm{}$). Experimental values of the inward convective velocity and diffusivity were $\sim {10}^3\left(\frac{r}{a}\right)$ cm/s and ∼ 300 ${\mathrm{cm}}^2$/s, respectively, which are of the order of neoclassical predictions. An internal disruption then occurred, which reduced on-axis impurities by frac23; and ended neoclassical-like transport. Carbon is also found to affect sawtooth dynamics dramatically by altering the central resistivity. The implications of these observations for ignited plasmas are discussed.

A damped oscillation at about 5 kHz was observed on the optogalvanic signals of a Ne hollow-cathode discharge on illumination by a pulsed dye laser at the resonant frequency of the $\mathrm{Ne} 2p_8-1s_5$ transition. The signal fits the formula $\Delta V\left(t\right)=V_0{e}^{-\frac{t}{\tau }}sin(\omega t+\theta )$, and the values of the parameters were determined for several positions of illumination and discharge currents. The oscillation originates from the ionization wave in the positive-column region, and a qualitative interpretation is presented based on the theory of striation.

An electrode pulsed to a large positive potential ($V>>\frac{k{T}_e}{e}$) in a collisionless magnetoplasma is observed to draw currents far in excess (10×) of the field-aligned electron saturation current prescribed by probe theory. The large currents are inferred to be due to anomalous cross-field transport caused by current-driven instabilities. Electric fields due to space-charge separation and anomalous conductivity lead in time to ion expulsion from the current channel and hence to density depletion and current collapse.

We study the structure of the reconstructed Au (100) surface, using a phenomenological Hamiltonian, including a many-body force term (the "glue"), carefully optimized to account for a vast variety of properties of solid and liquid gold. The optimal atomic configuration of (100) slabs is obtained by a molecular-dynamics strategy. We find that the glue term drives the reconstruction into a denser, quasitriangular surface layer. By variation of cell size and atom number, the lowest-energy configuration is found to be roughly (1×5), and more precisely (34×5), close to (26×48) suggested by experiment.

Results of a study of the Au (110) reconstruction using medium-energy-ion scattering with channeling and blocking are reported. The data show clear and direct evidence for a missing-row model, unequivocally demonstrate that the first-layer spacing undergoes a large contraction, and show the presence of distortions in deeper layers. This model is similar to one derived from analysis of low-energy electron-diffraction data, but differs qualitatively with conclusions from x-ray scattering and transmission electron diffraction.

The standard coagulation process is generalized to include the effects of fragmentation and a scaling description for the cluster size distribution is developed. The Smoluchowski rate equation is used to calculate the critical exponents describing the steady-state size distribution. Predictions of the scaling and the rate equation are tested by numerical simulations. The mean-field rate-equation results are found to be valid in $d>~1$ implying that the upper critical dimension $d_c$ is less than 1.

By means of quasielastic neutron scattering we show that the H-diffusion mechanism in ${\mathrm{Pd}}_{85}$${\mathrm{Si}}_{15}$${\mathrm{H}}_{7.5}$ is characterized by two well-separated regimes of jump rates, in clear contradiction to present ideas on diffusion in amorphous substances. A semiquantitative interpretation of the data is possible in terms of a two-state diffusion-trapping model. We find no evidence for the hypothesis that the network of diffusive paths in an amorphous substance has a fractal dimension.

The possibility of roughening in low-angle grain boundaries is investigated. By exhibiting an analogy between grain-boundary steps which do not have long-range strain and steps on solid surfaces, I argue that a grain-boundary roughening transition, of the same type as for solid surfaces, is possible. It is found that, as the grain-grain misorientation $\theta$ goes to zero, the energy of such a grain-boundary step diverges as ln ($\frac{1}{\theta }$). From this divergence I argue that, for sufficiently small $\theta$, the solid will melt before the grain boundary has a chance to roughen as the temperature increases.

A Si substrate is bombarded by 3-keV ${\mathrm{Ar}}^{+}$ ions. From time-of-flight spectra of resputtered Ar neutrals at various target temperatures, we conclude that Ar-bubble formation takes place in the amorphized-Si top layer. The bubbles form and open during etching. The average kinetic energy of the Ar atoms is in agreement with the calculated average potential energy of the Ar atoms inside the bubbles.

The linewidth of bulk plasmons in a rapid-quench ${\mathrm{Al}}_6$Mn quasicrystal is found to increase by ∼40% as compared with that observed in a thermally annealed crystalline ${\mathrm{Al}}_6$Mn sample. A narrower plasmon linewidth is also observed in a sputtered amorphous ${\mathrm{Al}}_6$Mn thin-film sample. We believe that the unusual plasmon line broadening in ${\mathrm{Al}}_6$Mn quasicrystals is a result of increased interband transitions due to the icosahedral symmetry of the quasicrystal, and not a consequence of lattice disorder.

A new technique has been developed for optical studies of amorphous solids to very high pressures. Raman spectra of Si${\mathrm{O}}_2$ glass measured at 8 GPa indicate a significant reduction in the width of the Si-O-Si angle distribution, which has been associated with a number of anomalous properties of silica glass under ambient conditions. Between 8 and ∼ 30 GPa irreversible changes in the Raman spectrum occur that are consistent with a shift in ring statistics in densified glass. The spectra suggest a breakdown in intermediate-range order at higher pressure.

Minima are found in the ac conductance (100 kHz) of $n^{-}-\mathrm{GaAs}-{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}-n^{+}-\mathrm{GaAs}$ capacitors at voltages corresponding to fractional fillings, frac13; and frac23;, of the lowest spin-split Landau level of an accumulation layer on $n^{-}-\mathrm{GaAs}$. These are the first observations of a fractional quantum effect in which electron motion is perpendicular rather than parallel to the $n^{-}-\frac{\mathrm{GaAs}}{{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}}$ interface.

Ionic cluster emission from Si by nitrogen-laser excitation is observed in a range of peak intensity from 50 to 500 MW/${\mathrm{cm}}^2$. Spectral analysis of time-of-flight measurements suggests the presence of ionic clusters within nanoseconds of irradiation. These clusters initially have a nearly uniform mass-to-charge ratio between frac32; and frac54; in units of ${\mathrm{Si}}^{+}$, and decompose through numerous channels of fragmentation. The result is in remarkable contrast with those of measurements in a time scale of more than 10 μs with the mass distribution corresponding to quasithermal equilibrium.

The spin polarization of true secondary electrons emitted from ferromagnetic transition-metal surface is expressed as a smooth "cascade" polarization plus a "fine-structure" part. Calculation of the latter for several Ni and Fe surfaces reveals pronounced structures, which agree well with hitherto unexplained experimental data and reflect the spin-dependent bulk band structure above the vacuum threshold.

With a simple model it is demonstrated that semiconductor quantum wells can exhibit motionally dependent binding. The dependence of binding on transverse motion results from mass mismatch at the quantum-well interfaces and can occur in both parabolic and nonparabolic systems. Accumulation layers on degenerate semiconductors such as $n-\mathrm{InAs}$ are shown to provide observational evidence for the effect. Implications for quantum-well experiments and applications are discussed.

Hydrogen iodide has been studied up to pressures of 70 GPa at low temperatures in a diamondanvil cell. Electrical-conductivity and optical measurements have been used to observe pressure-induced phase transitions which are interpreted as follows: First a metal-insulator transition takes place in the molecular solid; with increased pressure a metal-metal molecular-to-atomic transition occurs. An additional transition due to intrinsic impurities has been observed. Implications for metallic hydrogen are discussed.