Cross sections have been measured for the quasieleastic ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(e,e’p) reaction in the missing-energy region beyond the t+d threshold, which is domianated by the ${(3/2\mathrm{}}^{+}$ resonance. The data are compared with distorted-wave impulse-approximation calculations, which involve nuclear overlap functions derived from a cluster-distortion model extended to the continuum. The measured recoil-momentum dependence of the ${(3/2\mathrm{}}^{+}$ resonance can only be reproduced if an anomalous longitudinal-transverse ratio is taken into account.

A study of magnetic dipole strength in the rare-earth region and application to the 148–160Gd isotopes has been carried out. Within the Nilsson model, all two-quasiparticle $K^{\pi }$${=1\mathrm{}}^{+}$ configurations have been constructed and the M1 strength distribution has been calculated. Information on the total summed (non-energy-weighted) M1 strength is obtained. The distribution of orbital and spin M1 strength over different energy regions and over the whole rare-earth mass region was studied. Relations to quadrupole ground-state deformation are pointed out.

We discuss the interaction of localized solutions as they arise for the subcritical bifurcation to traveling waves. We find that for a large parameter range the localized solutions can interact so that they emerge after the collision with a size and shape unchanged compared to that well before the collision. The mechanism for this behavior, which is unusual for a strongly dissipative system, is qualitatively different from that associated with solitons for completely integrable systems. In accord with this we find that for other parameter values counterpropagating localized solutions can annihilate.

Lasing of the 488-nm Ar ii line has been demonstrated in the central 1.2 cm of a 4.5-cm diam rf-produced magnetoplasma at pressures of 1 Pa. The external rf antenna excites an m=1 whistler wave at the lower hybrid launch frequency which produces a highly ionized plasma. The inferred population inversion and the correspondence between measured wave phase velocity and the upper energy levels of the observed transitions suggest that Landau damping of the wave can selectively distort the electron distribution function at an energy equivalent to the phase velocity of the wave.

A dense background plasma is observed through computer simulation to reduce the phase velocity of the most unstable mode in a backward-wave oscillator which results in a strong efficiency enhancement. The relatively weak beam-backward plasma-wave instability introduced by the rippled waveguide wall is found to exert minimal impact on the interaction efficiency.

Interferograms of an underdense, preformed plasma which is irradiated with a line-focused laser beam show pronounced density perturbations. The interferograms are compared to simultaneous, gated images of second-harmonic emission. We observe a correlation between the spatial positions of the density perturbations and the peak of the second-harmonic emission. We interpret these phenomena as being emission from a local, nonlinear focus in the underdense plasma, rather than from the entire length of a filament.

The concept of the Pease-Braginskii current in a Z pinch is reexamined in the light of the anomalous resistivity that arises in a plasma when the electron drift velocity is greater than the ion sound speed. Radial profiles of density and current are derived on the assumption that anomalous resistivity will prevent the drift velocity from exceeding the sound speed. The value of the Pease-Braginskii current then depends upon the line density, and may be significantly greater than its classical value.

It is shown that, contrary to recent suggestions, the exponent ν, characterizing self-avoiding walks in a diluted lattice at the percolation threshold, is determined by a fixed point, different from the pure latttice one. The full phase diagram of this system is obtained by a real-space renormalization group and five nontrivial fixed points are identified. A field-theoretical treatment yields ν=(1/2+ε/42, with ε=6-d. All these results are supported by exact enumeration analysis.

The measured force as a function of separation between two mica surfaces immersed in a swollen lyotropic lamellar mesophase (interlamellar spacing 25–30 nm) is an oscillatory function of distance superimposed on a background attraction. The periodicity of the oscillations matches the bulk layer spacing at large surface separations, but it decreases at smaller separations, suggesting that the interlayer repulsion is due to fluctuations of the interfaces. The solid walls reduce these fluctuations, leading to a negative disjoining pressure.

The emission of high-energy photons from 150-GeV electrons traversing single crystals near axial directions is studied experimentally for Ge and, for the first time, also for Si. Enhancements relative to random up to 2 orders of magnitude are observed. For incident angles much less than the critical channeling angle ${\psi }_1$ a pronounced peak appears in the photon spectra near ∼85% of the electron energy for both the Si and the Ge crystals. The peak disappears for incident angles larger than ∼0.3${\psi }_1$. The experimental findings are compared to theoretical results.

The adsorption and growth of Ag on Si(100) at room temperature have been studied by scanning tunneling microscopy. The initial adsorption of Ag occurs at the two-fold bridge site in between adjacent Si dimer rows. Ag atomic chains are formed with preferred lengths. Metallic Ag islands form at coverages ≳0.5 ML, and develop into (111)- and (110)-oriented crystallites covering the entire surface at higher coverages.

The static dipole polarizabilities of aluminum clusters with up to 61 atoms, measured with a novel position-sensitive time-of-flight mass spectrometer, are at odds with jellium predictions for clusters with less than 40 atoms and agree for larger clusters revealing for the first time the nonjellium-to-jellium transition in a metal cluster system.

Localization behavior of the Anderson model with anisotropic diagonal disorder is both simulated numerically and calculated diagrammatically. As a function of the anisotropy parameter θ that interpolates between a one-dimensional randomly layered system and three-dimensional isotropic randomness, our results indicate the existence of a critical ${\mathrm{\theta }}_{\mathrm{c}}$ below which the wave function is localized even for infinitesimal values of randomness. Implications for observing the mobility edge in random superlattices are discussed.

We report measurements of the impurity-concentration and crystal-size dependences of the threshold field $E_T$ for charge-density-wave (CDW) depinning in ${\mathrm{NbSe}}_3$. These measurements establish that CDW’s in Ta-doped ${\mathrm{NbSe}}_3$ are weakly pinned. Size dependence of $E_T$ occurs when the transverse crystal dimensions become comparable to the transverse CDW phase-phase correlation length, resulting in a crossover from 3D to 2D weak pinning. A divergence of the T=4.2-K Ohmic resistance with decreasing sample thickness is attributed to diffuse scattering by crystal surfaces.

We have observed and described new optical transitions between magnetodonor states in InSb, assisted by optic-phonon emission. The phonon-assisted transitions provide a unique opportunity to investigate high excited states of the magnetodonor system (up to principal quantum number n=13), which simulates the hydrogen atom in gigantic magnetic fields. High-resolution data reveal the presence of additional excited magnetodonor states related to lower Landau subbands unobserved until present.

We have observed hot-electron electroluminescence in AlGaAs/GaAs heterodiodes. The resolution provided by the luminescence technique allows ballistically launched electrons to be clearly distinguished from those that have emitted one or more longitudinal-optical phonons. The electroluminescence consists of a series of peaks spaced by one-LO-phonon energy whose width is in agreement with a calculation of the energy distribution of the injected electrons. The position of the ballistic peak provides a new way to accurately measure the conduction-band offset in semiconductor heterostructures.

We show that the aging phenomena found in spin glasses and other complex systems can be reproduced by a hierarchical model of relaxation.

We performed light-scattering experiments on a mixture of hydrogen and argon. By varying the density of the sample, we can probe the range of reduced wave vectors in which Campa and Cohen [Phys. Rev. A 39, 4909 (1989)] predicted, in dilute disparate-mass gas mixtures, the onset of a mode supported by the light particles: the fast sound mode. The presence of the additional sound mode can be established most conveniently by analyzing ${\omega }^2$I(k,ω) rather than I(k,ω). Our results for the shift of fast and slow sound match the theoretical predictions very well.

Each weight change of three spinning mechanical gyroscopes whose rotor’s masses are 140, 175, and 176 g has been measured in inertial rotations without systematic errors. The experiments show that the weight changes on rotations around the vertical axis are completely asymmetrical: The right rotations (spin vector pointing downwards) cause weight decrease of the order of milligrams (weight), proportional to the frequency of rotations at 3 000–13 000 rpm. However, the left rotations do not cause any change in weight.

We use a rotating torsion balance to search for feeble forces arising from exchange of ultralow-mass bosons. Our limits on the differential horizontal acceleration of Be/Al or Be/Cu test-body pairs in the field of the Earth, Δ$a_{\perp }$=(1.5±2.3)×${10}^{\mathrm{-}11}$ cm ${\mathrm{s}}^{\mathrm{-}2}$ and Δ$a_{\perp }$=(0.9±1.7)×${10}^{\mathrm{-}11}$ cm ${\mathrm{s}}^{\mathrm{-}2}$, respectively, set improved bounds on interactions mediated by bosons with masses ranging between ${10}^{\mathrm{-}17}$ and ${10}^{\mathrm{-}6}$ eV.