The superdeformed band in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Gd}$ has been populated with various input angular momenta and excitation energies. These, together with all other available data, indicate that the necessary criterion for populating superdeformed bands is to form cold residual nuclei at spins higher than those where the superdeformed states become yrast. In addition, the decrease in the superdeformed band intensity as it is gated by higher-energy $\gamma$ rays does not support the predictions based on a recently proposed feeding mechanism of these states.

In electron-impact ionization of ${\mathrm{C}}^{3+}$ ions we found the first unambiguous experimental evidence for resonant-excitation auto-double-ionization processes. These involve capture of the projectile electron by the ion with simultaneous $K$-shell excitation and subsequent emission of two correlated electrons. The resonance strength measured for the $1s2s^{2}2p{}_{}{}^3{}_{}{}^{}P$ contribution is (2.0 ± 0.4) × ${10}^{-20\mathrm{}}$${\mathrm{cm}}^2$ eV. In addition, we resolved individual thresholds of excitation autoionization via states $1s2s2l$ and identified other resonant contributions to net single ionization.

A photoelectron hologram is a two-angle photoelectron diffraction pattern: Direct photoemission plays the role of the reference wave and the scattered waves are the object waves. When the hologram is created from the core-level photoemission of single emitting species on an ordered surface, a complete three-dimensional image of the surface structure surrounding the emitter can be reconstructed by Fourier transformation.

The transition to chaos through intermittency has been observed in a steady-state plasma system. Results from real-time signals, spectral analysis, and constructed Poincaré sections are used to confirm the existence of intermittency. Low-frequency $\frac{1}{f}$-type noise is also observed during the onset of chaos.

It is shown that transverse injection of a hypervelocity high-density spheromak plasmoid into a tokamak plasma may be a viable fueling scheme. Three important processes occur and are discussed individually: establishment of equilibrium, slowing down, and disassembly of the compact toroid.

We offer an explanation of the long-standing discrepancy between finite-size scaling theory and the observed temperature shift $T_{\lambda }-T_m$ of the specific-heat maximum in confined ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. On the basis of a renormalization-group calculation using Dirichlet boundary conditions we argue that a new size-dependent scaling variable should be employed. The theory agrees with the data in the regime $T_{\lambda }\gtrsim T_m$ without an adjustment of parameters and explains the gradual onset of finite-size effects far from $T_{\lambda }$.

The polarization dependence of the viscosity of spin-polarized liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been determined in the temperature range $75<T<\mathrm{}300\mathrm{}$ mK and the polarization range $\Delta <0.35\mathrm{}$. We find an increase in the viscosity, which can be described as $\eta \propto 1+\alpha {\Delta }^2$ with $\alpha =4.0\mathrm{}\pm 1.5$, at a pressure of 27 bars. This increase is expected from the ratio of the cross sections for $s$-wave and $p$-wave scattering. It is rather surprising, however, that there is no temperature dependence of $\alpha$.

Mobile rigid rods grafted on an interface are treated both by Onsager-type and Monte Carlo approaches. Symmetry arguments are presented which show that, unlike the case of hard rods in bulk, no orientational "standing-up" transition occurs: Attractive forces between rods are necessary for a discontinuous change in alignment. These conclusions are confirmed by Monte Carlo simulations and are discussed in the context of recent controversies concerning the "expanded" to "condensed" phase transition in adsorbed surfactant monolayers.

The surface sensitivity of second-harmonic generation has been utilized to measure the spatial and frequency dependence of the local field generated at the surface of a nearly free-electron metal by an external electromagnetic field. The second-harmonic signal as a function of film thickness for a thin layer of alkali metal deposited onto a single-crystal substrate produces a direct image of the damped oscillatory longitudinal field generated in the metal in response to the external field.

Strongly coverage-dependent outward relaxation and enhanced in-plane vibrational amplitudes of metal surface atoms have been observed from S- and Cl-covered Ni(001) and Cu(001) by means of temperature- and polarization-dependent surface extended-x-ray-absorption fine-structure measurements. These results explicitly demonstrate the weakening of both interlayer and intralayer metal-metal substrate bonds. A model based on adsorbate-metal charge rearrangement explains these chemisorption-induced changes in the geometric and dynamic properties of the metal surface.

The quasielastic light-scattering spectrum of cooled fused-silica optical fibers has been measured by heterodyne spectroscopy in the frequency range 75 kHz to 75 MHz at temperatures from 20 to 293 K. Below 160 K, the conventional Rayleigh scattering becomes undetectable and the main scattering component has a spectrum given by $S(\omega ,T)\sim {\omega }^{-\alpha }$, where $0.5<\mathrm{}\alpha \mathrm{}\left(T\right)<1\mathrm{}$. The scattered power has the temperature dependence expected for activated structural transitions.

Time-of-flight distributions of sputtered Au atoms have been measured under 4 ke V ${\mathrm{I}}^{+}$ and 8 keV ${\mathrm{I}}_2^{+}$ impact. The results show that a developing thermal spike contributes to the sputtering yield. It is higher under ${\mathrm{I}}_2^{+}$ bombardment but the measured temperature obtained from Maxwell-Boltzmann fits is lower, suggesting a lower effective surface binding energy $U_0$ for ${\mathrm{I}}_2^{+}$ bombardment. A correlation between spike temperatures and $U_0$ is discussed.

The probability for resonant tunneling through a quantum well is calculated for a model including electron-phonon coupling. The interaction of the tunneling electron with optic phonons produces resonant transmission sidebands, which are readily observable in $I-V$ characteristics. Our results confirm the recent experimental observation of phonon-assisted resonant tunneling in GaAs.

A theory of magnetic quantum oscillations in the nuclear spin-lattice relaxation rate, $T_1^{}{}_{}{}^{-1\mathrm{}}$, in quasi-two-dimensional conductors at low temperatures and under strong magnetic fields is presented. We show a close similarity between the magnetic field dependence of $T_1^{}{}_{}{}^{-1\mathrm{}}$ and that of ${\rho }_{\mathrm{xx}}$ in the quantum Hall effect. The shape and the amplitude of the oscillations in $T_1^{}{}_{}{}^{-1\mathrm{}}$ depend strongly on band anisotropy, electron mean free path, spin Larmor frequency, and temperature, and may provide rich information on the sample parameters.

Quantum-well states have been observed with angle-resolved photoemission for Ag overlayers with thicknesses up to 40 monolayers epitaxially grown on Au(111). These states are observed within an energy window of 1 eV. The complementary system, Au on Ag(111), exhibits no such states. The results can be explained in terms of the band-structure mismatch between Au and Ag. The coherence length of the states and quasibound quantum-well resonances will be discussed.

The $1s-2p(m=+1\mathrm{})\mathrm{}$ hydrogenic transition in magnetic fields up to 20 T for shallow donor impurities confined in 138-Å GaAs wells in AlGaAs/GaAs multiple-quantum-well structures has been used to investigate the electron-optical-phonon interaction. A resonant "pinning" behavior has been observed at energies well below (∼50 ${\mathrm{cm}}^{-1\mathrm{}}$) that of the long-wavelength optical phonons of GaAs. It is suggested that these surprising results may be explained by interaction with near-zone-boundary longitudinal-optical phonons activated by the superlattice.

${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ Mössbauer spectra of ${\mathrm{Ta}}_{0.8}$${\mathrm{Fe}}_{0.2}$${\mathrm{S}}_3$ recorded as a function of applied magnetic field at 4.2 K show that a reversible phase transitions occurs at $H_c\simeq 15$ kOe. Magnetization measurements confirm this observation. The experimental results are consistent with some form of antiferromagnetic ordering for $H>\mathrm{}{H}_c$, inferring that charge-density waves and spin-density waves may coexist in this material.

Using an Anderson impurity description of the high-$T_c$ superconductors, we study the character of the states closest to the Fermi level. In a kind of phase diagram involving the Cu $d-d$ Coulomb interaction ($U$), the charge-transfer energy ($\Delta$), and the hybridization ($T$), we show under which conditions the singlet, triplet, or delocalized ligand hole states are closest to the Fermi level. For reasonable values of $T$ the lowest-energy hole states are local singles (${}_{}{}^1{}_{}{}^{}A_{1g}^{}{}_{}{}^{}$) of primarily $d^9\mathit{L}$ character for $U>\mathrm{}\Delta$ and local triples (${}_{}{}^3{}_{}{}^{}B_{1g}^{}{}_{}{}^{}$) of primarily $d^8$ character for $U<\mathrm{}\Delta$.

The $a-b$-plane penetration depth $\lambda \mathrm{}\left(T\right)\mathrm{}$ in Y${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ films, determined from kinetic inductance measurements, follows the temperature dependence of weak-coupling mean-field BCS theory near $T_c$ to within ∼0.5 K of $T_c$, resolution limited either by homogeneity or for the thinnest films by phase fluctuations. The Kosterliz-Thouless transition in a thin film is the first observation in a clean type-II superconductor, noted by the universal superfluid jump and the algebraic-decay law with a square-root cusp exponent.

Accurate measurements of $\frac{2e}{h}$ by means of the ac Josephson effect have been carried out by the use of weak links of a high-$T_c$ superconductor, Y-Ba-Cu-O, of macroscopic dimensions. The result, $\frac{2e}{h}=483595.0\mathrm{}\pm 1.7$ GHz/V, differs, in relative value, from that obtained by accurate measurements in metallic superconductors by 5.6 × ${10}^{-6\mathrm{}}$.