The interaction between $〈100〉$ climb-induced dislocation networks and a naturally occurring deep level (the $\mathrm{DX}$ center) in ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ has been analyzed by scanning deeplevel transient spectroscopy. The concentration of $\mathrm{DX}$ centers was observed to decrease markedly in the vicinity of climb-induced $〈100〉$ networks, but remained nearly unchanged near glide-induced $〈110〉$ dislocation networks.

Single-crystal silicon samples have been made disordered by irradiation with pulses from a frequency-quadrupled neodynium-doped-yttrium-aluminum-garnet laser with ${10}^{-8\mathrm{}}$-s pulse length. We have studied the resulting amorphous layer by transmission electron microscopy and He-ion backscattering. Irradiation with longer-wavelength pulses restored the disordered layer to its original crystalline state. This order-disorder laser-radiation-induced transition is repeatable.

We report the first observation of ESR of negative ions in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. The signals exhibit pressure-dependent integrated signal intensity and line shape. These data are tentatively interpreted by considering the hyperfine coupling of the bound electron with the surrounding ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ nuclear moments.

We have investigated the orientation dependence of the structure near the boron $K$ edge in electron-energy-loss spectra from hexagonal boron nitride. Angular distributions of spectra recorded from crystals with $c$ axis tilted at 45° to the beam allow us to determine unambiguously the $\pi$ and $\sigma$ character of the final states at different energies. Results are in quantitative agreement with a model based on hydridized atomic orbitals.

A model inverse dielectric matrix is used to calculate the electronic response to impurity potentials in silicon. We show that local-field effects are strong on the scale of interatomic distances and that they give rise to relevant quantitative effects on the binding energies and wave functions of both deep and shallow impurities.

We study fluctuations in a fluid with a stationary, linear shear. We find that the pair-correlation function gains a long-ranged part. The Brillouin components of scattered light are enhanced or reduced compared to equilibrium depending on the scattering angle. The Landau-Placzek ratio no longer holds and the total scattering intensity is $k$ dependent. We suggest a simple light-scattering experiment to test our predictions. The new features are explained by the differential attenuation of sound modes.

The discrepancy between the measured and calculated extended-x-ray-absorption fine structure amplitude in ${\mathrm{Br}}_2$ molecules, the best documented case, is found to be due to an error in the experimental result. New measurements show good agreement with single-particle calculations at low energies near the $K$ absorption edge and a value about 20% below the calculated one at high energies in agreement with the expected multielectron correction to the single-particle calculation.

Using polarized light and angle-resolved photoelectron spectroscopy, we have shown that oxygen is bonded in an ordered (1×1) configuration on Al(111). For this model system, we have determined the symmetry and dispersion of the threee oxygen derived bands. We find two even and one odd band with respect to the ($1\overline{1}0$) mirror plane. A disordered oxide film shows no dispersion and different oxygen binding energies.

CeSe and CeTe are found by neutron diffraction to be type-II antiferromagnets with the moment along the propagation vector. The phase transitions are continuous with the critical exponent for the magnetization $\beta =0.36\mathrm{}\pm 0.02$. This constitutes a violation of the $\epsilon$-expansion predictions of Bak, Krinsky, and Mukamel, which hitherto have been successfully applied to a number of $n>~4$ systems and according to which the transitions should be of first order.

An expression for the Kolmogorov entropy has been derived. Excellent agreement between a probability description and direct dynamical computations has been found.

A recently proposed mass formula for the muon is extended to $\tau$ and other heavy leptons. It is postulated that a quantized magnetic self-energy of magnitude $\frac{3}{2}{\alpha }^{-1\mathrm{}}{n}^4{M}_e$, where $n$ is a new quantum number, be added to the rest mass of a lepton to get the next heavy lepton in the chain $e$, $\mu$, $\tau ,\cdots$, with $n=1\mathrm{}$ for $\mu$, $n=2\mathrm{}$ for $\tau$, etc. I predict $M_{\tau }=1786.08\mathrm{}$ MeV, and for the next lepton $M_{\delta }=10\mathrm{}293.7$ MeV.

We improve the sufficient condition for uniqueness of the solution of the elastic unitarity equation for given differential cross section. Uniqueness is proved for $sin\mu <0.9577\mathrm{}$, which is close to the conjectured condition $sin\mu <1\mathrm{}$. Here $sin\mu$ is the supremum of an integral determined by the cross section. Improved conditions depending on the infinum of the integral are also obtained.

Qualitative features of the $\gamma$-emission spectrum from nuclear states in the 50-MeV excitation energy range to states in the giant-dipole-resonance region are described. Properties of the initial- and final-state structures are deduced.

The intensity distributions of F $K\alpha$ satellites produced by 84-MeV ${\mathrm{N}}^{4+}$ bombardment displayed a significant chemical effect. The dependence of the intensity distributions of several fluorides on the chemical environment is discussed in relation to the Pauling bond ionicity or covalency. A refilling of vacancies by ligand valence electrons prior to the x-ray emission accounted for the observed satellite distributions for the compounds used.

We suggest that the intensity correlation function could be an important tool in the study of atomic cooperative behavior because it contains predominantly components at 0, $\pm 4\Omega$ in the limit of large Rabi frequency ($2\Omega$) and large cooperation number. This is in contrast with the single-atom prediction where the intensity correlation function contains only frequency components at 0, $\pm 2\Omega$. The master equation for the collective system is solved analytically in the secular approximation.

The weighted mean square of the Navier-Stokes equation is mimimized with a complete set of realizability inequalities as constraints. Expansion of moments in complete orthogonal functions leads to successive approximations without ever involving moments of order higher than 4. Alternatively, the expansions may be in Wiener-Hermite kernels, thereby automatically satisfying the realizability constraints. The approach extends to other classical and quantized systems with polynomial nonlinearity.

Experimental observation and studies of a new type of cold electrostatic mode near the ion-ion hybrid frequency are presented. The resonance cone behavior associated with this mode is verified. The wave dispersion relation has been measured which shows a clear resonance behavior near the hybrid frequency. Associated with the mode, strong electron Landau damping by bulk electrons and equally strong ion damping near the ion-ion hybrid resonance are observed. This type of mode should be readily excited in high-field devices ($B_0\gtrsim 30$ kG).

Magnetic pickup loops inserted into the Macrotor tokamak have shown a broad spectrum of oscillation in $B_r$ and $B_p$ up to $f\approx 100$ kHz. The high-frequency ${\tilde{B}}_r$ have short radial and poloidal correlation lengths $L<\mathrm{}5\mathrm{}$ cm, in contrast with the usual Mirnov oscillations with $f\approx 7$ kHz and $L\gg 5$ cm. The observed magnitude $\frac{\Sigma \left|{\tilde{B}}_r\right|}{B_T}>{10}^{-5\mathrm{}}$, where the summation extends over all $f>\mathrm{}30\mathrm{}$ kHz, is in the range in which such radial magnetic perturbations may be contributing to anomalous electron energy transport.

Three-dimensional, electromagnetic computer simulation experiments are presented showing the evolution of plasma columns subjected to external electric and magnetic fields. The results of two experiments are presented here. In the first, self-confinement is achieved; in the second, as instability arises which drives the plasma into a helical configuration.

The existence of a special set of cusp-shaped, stable, force-free plasma equilibria with finite pressure and flow velocity is demonstrated. They are confined by surface currents.