Production of projectile Rydberg states in fast-ion-foil collisions is shown to exhibit a pronounced target-thickness dependence, proving that Rydberg states are not predominantly formed by direct capture of target electrons. Instead, it is proposed that ionized projectile electrons can undergo transition back to Rydberg states when the ion emerges from the foil.

Spheromak dynamics is studied for a zero-$\beta$ plasma by a three-dimensional magneto-hydrodynamics simulation code. The growth rate of the tilting instability is found to be of the order of $10{\tau }_{\mathrm{A}}$ (Alfvén transit time) and, more interestingly, once tilt occurs, the spheromak field reconnects three dimensionally with the vertical field, thus leading to a disruptive deformation of the spheromak.

In a stationary recombining hydrogen plasma, resonance fluorescence of the ${\mathrm{H}}_{\alpha }$ line is measured by the laser-induced fluorescence method. Population inversion between $n=2\mathrm{}$ and $n=3\mathrm{}$ levels is verified by the observation of the fluorescence reduction. Marked inversion is obtained only in the upstream region of a flowing recombining plasma. Extinction of the inversion towards the downstream region is explained by the effect of the plasma opacity.

The authors present the first detailed investigation of the ablative acceleration of planar targets while simultaneously using high irradiance (${10}^{14}$ W/${\mathrm{cm}}^2$), large focal diameters (1 mm), and long laser pulse duration (3 nsec). Included are measurements of target preheat, ablation pressures, and uniformity achieved under these conditions. Targets were accelerated to high velocities with velocity profile uniformity approaching that required for high-gain pellet implosions.

By means of neutron inelastic scattering the dispersion of collective density fluctuations in a topologically disordered solid has been investigated for momentum transfers $Q$ near $Q_p$, where the static structure factor has its first maximum. A nonzero minimum is found near $Q_p$. The dependence of the observed peaks in the dynamic structure factor $S(Q, \omega )$ on heat treatment is discussed and the results are compared with recent computer simulations and model calculations.

By means of ESR in a high magnetic field the hyperfine states of a gas of spin-polarized atomic hydrogen are directly probed. This allows a direct determination of the spin-state populations and nuclear polarization. The unusual ESR line shape is attributed to field inhomogeneities. The temperature of the gas was determined by use of ESR with no indication of nonequilibrium due to Kapitza resistance. Recombination rates between hyperfine states could be determined.

Measurements of the mass-density fluctuations associated with the first-order nematic-to-smectic-$C$ transitions in $\overline{8}\mathrm{S}{5}_{1-x}-\overline{7}\mathrm{S}{5}_x$ mixtures are reported. This binary system exhibits nematic, smectic-$A$, and smectic-$C$ phases, and a multicritical point $x_{\mathrm{NAC}}$. As a function of decreasing temperature for $x>\mathrm{}{x}_{\mathrm{NAC}}$, the scattering in the nematic phase evolves from smectic-$A$ to pretransitional smectic-$C$ fluctuations described by a Lifshitz model of Chen and Lubensky. Important discrepancies remain with the predictions of the model near $x_{\mathrm{NAC}}$.

Monte Carlo simulations have been carried out to study the effect of temperature on the growth kinetics of a circular grain. As predicted by $d=3\mathrm{}$ theories of domain kinetics, the circular domain shrinks linearly with time as $A\left(t\right)=A_0-\alpha t$, where $A_0$ and $A\left(t\right)\mathrm{}$ are the initial and instantaneous areas, respectively. However, in contrast to $d=3\mathrm{}$, the slope $\alpha$ is strongly temperature dependent for $T>~0.6T_c$. An analytical theory which considers the thermal fluctuations agrees with the $T$ dependence of the Monte Carlo data in this regime.

Superconductivity has been discovered in polycrystalline rhodium with $T_c=325\mathrm{}$ μK and $B_c\mathrm{}(T=0\mathrm{})=49\mathrm{}$ mG. The investigated samples exhibit full Meissner effect and show behavior typical of a type-I superconductor. The influence of sample purity has been studied, and the possible influence of spin fluctuations is discussed.

Nuclear-magnetic-resonance measurements in incommensurate ${\mathrm{Rb}}_2$Zn${\mathrm{Br}}_4$ show the existence of regions where the modulation wave is floating. The floating regions coexist with other regions where the modulation wave is static. Impurity phase pinning and a roughening of the modulation wave at higher temperatures is proposed to account for these effects.

A new measurement of the $\pi \to e\nu$ branching ratio yields $\frac{\Gamma (\pi \to e\nu +\pi \to e\nu \gamma )}{\Gamma (\pi \to \mu \nu +\pi \to \mu \nu \gamma )}=(1.218\mathrm{}\pm 0.014)\times {10}^{-4\mathrm{}}$. The measured value is in good agreement with the standard-model prediction incorporating electron-muon universality.

The energy-resolved spin polarization $P$ of secondary electrons from Ni(110) has been measured with high energy resolution. At the lowest kinetic energy $P$ reaches a maximum of (17±2)% which is significantly higher than the mean conduction-band polarization (5.5%). Within about 3 eV towards higher kinetic energy the spin polarization decreases to about 8% and displays pronounced structures at higher energies. Spin-dependent electron-hole-pair excitations are suggested to be responsible for the observed spin polarization.

A laser-scanning technique capable of probing the local current density in Josephson junctions has been used to study the current distribution and inhomogeneity of both high-and poor-quality junctions. Results from a high-quality tunnel junction are in good qualitative agreement with theory. The technique is also shown to be useful to study superconduting-normal-superconducting structures and bridge-type weak links.

The mean square distance reached after $t$ random-walk steps on a percolating cluster is shown to behave as $t^{\frac{2}{(2+\theta )}}$ (instead of $t$) for short times (for which the cluster is seen to be self-similar). The exponent $\theta$ is related to that describing the dc conductivity near percolation. Averaging over all clusters yields the ac conductivity and dielectric constant near percolation in the high-frequency limit, when the polarization of the medium is unimportant.

On the basis of a numerical study of a mean-field free-energy surface, the authors propose that an isotropic Heisenberg spin-glass has no irreversibility. The field-cooled and zero-field-cooled states are the same and magnetic hysteresis is absent. The authors show how Dzyaloshinsky-Moriya and uniaxial anisotropy effects lead to irreversibility. Hysteresis loops exhibit sharp jumps at constant field only when both microscopic anisotropy and a ferromagnetic tendency are present.

The electrical field dependence of Wannier resonances in crystals is calculated numerically and it is shown that the resonance widths oscillate strongly as conjectured by Avron.

The large-scale stochasticity threshold for Hamiltonians with two degrees of freedom with only one primary resonance can be analytically estimated because of the quite steep growth of the stochastic layer of this resonance. For Hamiltonians without primary resonance, the threshold is computed by available techniques after canonical transformations. Thus the first analytical estimate of the threshold is obtained for the Hénon-Heiles Hamiltonian and an example of Walker and Ford.

A breather soliton of the sine-Gordon equation is shown to behave stochastically in the presence of an external oscillating field, which leads to random pair creations of kink and antikink solitons.

It is shown that $\int {\left|V\right(\overrightarrow{\mathrm{x}}\left)\right|}^{\frac{3}{2}}{d}^{3}x>\left(\frac{{\pi }^2}{4}\right){\left(\frac{3{\hslash }^2}{2m}\right)}^{\frac{3}{2}}$ is a necessary condition for one or more normalizable bound-state solutions to the nonrelativistic Schrödinger energy-eigenvalue equation for any potential function $V\left(\overrightarrow{\mathrm{x}}\right)$ such that the integral is finite. Moreover, for potentials such that $\int {\left|V\right(\overrightarrow{\mathrm{x}}\left)\right|}^{\frac{3\gamma }{2}}{d}^{3}x$ is finite for a value or values of $\gamma >1\mathrm{}$, the magnitude of a negative energy eigenvalue is related to the latter integral by a general inequality derived here.

Power spectra and phase-space trajectories for a sine-wave-driven Josephson-junction analog are measured, showing period-doubling bifurcations and transition to chaos. The total noise power follows closely a universal power law with a critical exponent σ and the average bandwidth in the chaotic regime scales with a universal number $\beta$, both in good agreement with theoretical predictions. Measured values of other universal numbers are reported.