A systematic study of the hyperfine structure of $5snd$ ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}D_2^{}{}_{}{}^{}$ states of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Sr}$ was carried out by Doppler-free two-photon excitation. In the region of strong singlet-triplet mixing around $n=16\mathrm{}$, the hyperfine structure exhibits a marked $n$ dependence which is related to the amount of singlet-triplet mixing.

Measured Fe i densities in the edge region of the impurity study experiment (ISX-$B$) tokamak in Ohmic and neutral-beam-heated discharges are consistent with calculated densities, if one assumes that sputtering of the stainless-steel walls by charge-exchange neutrals is the dominant production mechanism. Fe i and Ti i densities observed during plasma shift experiments indicate that the limiters play only a minor role in impurity production in ${\mathrm{D}}_2$ discharges. This also suggests that most metals are sputtered from the walls.

Spectroscopic observations on the ISX-$B$ (impurity study experiment) tokamak indicate that most of the metallic impurities come from the wall in Ohmically heated discharges in which the plasma is kept centered in the vacuum chamber. These impurities appear to accumulate during the quasi-steady-state part of the discharge if the working gas is deuterium but not if it is hydrogen.

We show that nonpropagating density ripples are produced in a flowing laser-produced plasma corona by the ponderomotive force of the incident light and the light reflected from the critical surface. These ripples are not related to instability but rather are an equilibrium feature of the flow. Under certain conditions they can significantly increase specular reflection and reduce the amount of light reaching the critical surface.

The time-dependent spectrum of 1.053-μm light reflected from spherical targets has been measured for intensities between 0.4×${10}^{15}$ and 10×${10}^{15}$ W/${\mathrm{cm}}^2$. The spectra are primarily shifted to the blue and are consistent with a Doppler-shift model. When compared with hydrodynamic code simulations, they place restraints on models for heat transport and suprathermal electron transport.

It is shown that through nonlinear model coupling processes long-wavelength, low-frequency strong $\overrightarrow{\mathrm{E}}\times \overrightarrow{\mathrm{B}}$ turbulence can stabilize short-wavelength, high-frequency Farley-Buneman modes in a weakly ionized low-pressure convecting plasma. Favorable comparisons are made with experimental observations.

The (linearized) hydrodynamics of a layered film configuration is considered for propagating modes of third sound. The theory is applied to (normal) ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and H↓-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixture film systems. When both films are superfluid, two propagating modes at each wave vector $k$ will be observed. Thus, the detection of superfluid onset in the H↓ film should be direct and unambiguous. When the upper film is normal, an easily measurable shift in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ third sound velocity, directly related to the physical characteristics of the normal film, will be observed.

New measurements near $T_{\mathrm{sg}}$ characterize the heat-capacity anomaly associated with spin-glass ordering. There are no discontinuities in the heat capacity or its temperature or field derivatives but there is a relatively sharp anomaly in the field derivative and a broad anomaly in the temperature derivative. A failure of thermodynamics to predict correctly the relation between heat capacity and magnetic susceptibility may be a manifestation of the "nonergodic" behavior of disordered systems.

A classical time-of-flight method was used to determine the temperature of evaporated Si atoms and thus the lattice temperature of Si during pulsed laser annealing. The resulting temperatures between 1200 and 3000 K for energy densities between 1.0 and 2.5 J/${\mathrm{cm}}^2$ clearly support a strictly thermal annealing model including melting of the surface region of Si.

Exact averaged equations for spin relaxation in infinite-ranged spin-glasses are derived. It is shown that, in general, time-persistent terms in both correlation and response functions cannot be treated as purely static order parameters. A dynamic stability criterion for static solutions is derived. In the marginally stable solution dynamic correlations decay algebraically $\sim t^{-\nu }$ below $T_c$, with an exponent which decreases continuously with temperature, $\nu \mathrm{}\left(T\right)=\frac{1}{2}-{\pi }^{-1\mathrm{}}\left(\frac{1-T}{T_c}\right)+O\left({\left(\frac{1-T}{T_c}\right)}^2\right)$, in disagreement with previous predictions ($\nu =\frac{1}{2}$).

The positronium fraction is measured in Ge for positron implant energies from 25 to 5025 eV and sample temperatures from 300 to 1050 K. A simple one-dimensional diffusion model is fitted to this data to extract the positron diffusion constant ($D_{+}$) in three Ge single crystals. The abrupt decrease in $D_{+}$ between 600 and 850 K cannot be explained by the mechanism established for metals: positron-vacancy trapping. An interpretation in terms of a transition from a free positron to a small positron-polaron state is proposed.

A direct relation between Feder's normal mode coordinate for solid squaric acid (${\mathrm{H}}_2$${\mathrm{C}}_4$${\mathrm{O}}_4$) and the line separation $\Delta \sigma$ in high-resolution ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR is established. The temperature variation of $\Delta \sigma$ fits to a first-order phase transition. At the phase transition the ${\mathrm{C}}_4$${\mathrm{O}}_4$ unit is shown to undergo a change in its electronic structure.

The core-valence-valence Auger line shapes of free-electron metals are evaluated with use of a change of mean-field model for the initial-state interactions. Significant many-body effects are (i) excitonic distortion of the initial-state orbitals, (ii) the Anderson orthogonality effect, (iii) replacement transitions, and (iv) shakeoff transitions. Comparison of the theory with Li data suggests that both many-body effects and band effects play major roles in determining Auger line shapes.

The optical-orientation technique is applied to clarify the electronic valence-band structure of gold near the $L$ point. Interband energies which are unobservable in standard photoemission experiments have been determined. They show that existing relativistic band calculations are accurate within a few tenths of an eV in the $k$ region considered.

Results are presented and interpreted for the zero- and finite-temperature excitation spectrum of ferromagnetic Ising-Heisenberg chains, as probed by dynamic form factors. Finite-chain calculations demonstrate the occurrence of a thermally induced resonance centered around zero frequency, and a broadening of the magnon and two-magnon bound-state resonances at low $T$. The occurrence of bound states in the associated transitions demonstrates the failure of finite-order magnon perturbation theory.

Surface-absorption fine-structure studies for CO and NO on Ni(100) exhibit two pronounced resonances above the C, N, and O $K$ edges. A strong polarization dependence of these resonances, which correspond to a $\sigma \to \pi$ discrete absorption and a $\sigma \to \sigma$ shape resonance, allows the precise determination of molecular orientation. Both molecules are found to be aligned along the surface normal within 10°.

We report the first observation of an energy barrier in the transition of a metastable free hole to the self-trapped state. The lifetime of the free hole was monitored by using electron paramagnetic resonance to measure the competition between self-trapping and trapping at such substitutional ions as ${\mathrm{Cu}}^{+}$. Over the range 4.5 to 30 K, the lifetime against self-trapping decreases with increasing temperature, with an activation energy of 1.7 meV.

We propose that the cohesive energies of simple metals can be accurately predicted solely from atomic kinetic energy terms. In this fashion, we are able to determine the cohesive energy of twenty simple metals to an accuracy better than 15%. Moreover, we are able to quantify orbital contributions to cohesion.

Methods for complete calculation of cosmological baryon-number generation in the hot big-bang early universe are outlined and are applied to several SU(5) models. Effects of several baryon-number-nonconserving bosons and the presence of nonthermalizing modes are treated.

A hard intrinsic charm component of the nucleon, as recently deduced from the charm hadroproduction data, is shown to account for the anomalously small scale breaking ($\Lambda \simeq 0.1$ GeV) observed in the $\mu N$ data of Norton et al. (European Muon Collaboration), without affecting the results ($\Lambda =0.3-0.4\mathrm{}$ GeV) of the SLAC-MIT (Stanford Linear Accelerator Center-Massachusetts Institute of Technology) or CDHS (CERN-Universität Dortmund-Universität Heidelberg-Centre d'Etudes Nucléaires de Saclay) Collaborations.