The surface peak, observed in backscattering-channeling experiments, has been measured as a function of projectile (${\mathrm{He}}^{+}$) energy on a clean W(100) crystal. We show that the intensity of the surface peak is in good agreement with classical models of channeling. Furthermore, we deduce an upper limit of 6% for the relaxation of the W(100) surface.

It is shown that a linear specific heat in amorphous systems at low temperatures is a general consequence of the nonapplicability of the third law of thermodynamics. A hydrodynamic formula relating the pair density of states of Anderson et al. to diffusive and mechanical coefficients, determinable under favorable conditions by Rayleigh light scattering is also proposed.

Critical temperature $T_c$ and transition width $T_{\varphi }$ of 5-μm ${\mathrm{Nb}}_3$Sn samples (chemical vapor deposition) have been measured as functions of 25-MeV oxygen irradiation below 30 K and isochronal annealing up to 410 K. After the known strong reduction, $T_c$ shows at high fluences leveling-off effects, a flat minimum followed by an increase revealing competing superimposed disorder mechanisms. Significant recovery of $T_c$ and $T_{\varphi }$ to lower values is observed. Results are discussed in terms of atomic disordering and compared to $n$ and He experiments at room temperatures.

The creation probability of soliton-antisoliton pairs due to quantum-mechanical tunneling in the presence of an electric field in charge-density—wave condensates is calculated. This process gives rise to an additional electric conductivity strongly nonlinear in the electric field, which may account in part for the anomalous conductivity observed in Nb${\mathrm{Se}}_3$.

The high polarizability of the $3d$ shells in Ba, La, and Ce leads to a dynamically screened $E_g\to 4f$, $\hslash \omega$ electron-photon coupling, having pronounced resonances due to intermediate $3d^{9}4f^2$ levels. We qualitatively and even quantitatively reproduce the asymmetric bremsstrahlung intensity resonances experimentally observed by Liefeld, Burr, and Chamberlain.

The very large deviations from Fresnel diffraction due to Coulomb excitation seen in heavy-ion scattering can be reproduced by a polarization potential which is derived without making the adiabatic approximation. This potential is predominantly imaginary.

We have measured the shape of the $p+p$ cross section at five energies from 6-10 MeV (lab) using solid targets. Our results resolve discrepancies in values of the shape-sensitive central $p$-wave parameter ${\Delta }_c$ obtained from the gas-target data of other groups. We agree particularly well with data which had suggested difficulties in reconciling both high- and low-energy data with one-boson-exchange models of the nucleon-nucleon interaction.

We separate the (decoupled) perturbation equations for the radiative components of perturbing fields of spin $s=0, \frac{1}{2}, 1, \mathrm{and} 2$ in an arbitrary type-$D$ vacuum background, realized in Plebański-Demiański coordinates.

We determine the mass and width of the $A_1$ meson using a unitary and analytic isobar parametrization.

The process ${\mu }^{-}+\mathrm{nucleus}\to e^{-}+\mathrm{nucleus}$ is examined within the framework of gauge theories. We find that the rate for this reaction is much larger than what one might naively expect for a large class of models which allow the decay $\mu \to e+\gamma$. Further experimental search for this rare process is strongly urged.

We have calculated the deuteron electromagnetic form factor to all orders of $\frac{q^2}{M^2}$ in the impulse approximation. Our results are compared to the data for selected deuteron wave functions. We also extract the ultrahigh-$q^2$ limit of our results, and obtain most naturally the same $q^{-10\mathrm{}}$ falloff predicted by the quark model.

Charged pions emerge from roughly 70% of the neon interactions that produce stars in nuclear emulsions at incident energies between 100 and 280 MeV/nucleon. The chargedpion multiplicity averaged 2.8 per pion-producing event. The data are in apparent disagreement with predictions based upon the independent-particle model. Agreement is found with the pion-condensation model of high-density nuclear states as formulated by Kitazoe et al.

It is shown that the photoelectron angular distribution of $s$ electrons in an open-shell atom, having outer configuration $n{s}^{2}n{p}^q$, is not described by the asymmetry parameter $\beta =2\mathrm{}$, as predicted by more approximate theories, but has dramatic variations with energy even within $\mathrm{LS}$ coupling. Calculations for the $3s$ subshell in Cl are presented as an example.

It is experimentally demonstrated in the ATC device that, with appropriate adjustment of the external magnetic circuitry, the tokamak plasma may be stable for two different major radii. The dynamics of the transition between the two equilibria involves a faster compression and expansion of the plasma than is practical in the monostable case; this may be useful in the Artsimovich-Furth-Ellis axisymmetric magnetic pumping scheme.

A suprathermal electron beam is injected parallel to $\overrightarrow{\mathrm{B}}$ in a low-$\beta$ plasma. The sharp space-potential drop across the surface of the beam generates a strong cross-field current which in turn drives a modified two-stream instability at the lower hybrid frequency. Intense stochastic ion heating is observed with the onset of the instability, and the heating rate is found to be proportional to the wave energy.

A new method that includes long-range interactions is described and used to compute the site-occupancy correlation in a one-dimensional ionic conductor. The method is applied to hollandite, for which the ions move within independent channels. Through this analysis, we deduce specific information about the interionic potential from experimental data on cationic order. Because of the peculiar screening provided by this material, the potential between mobile ions decays quickly for the first few lattice sites and has only a weak Coulomb tail.

I have performed molecular-dynamics calculations for $\alpha$-AgI at 563 K using a realistic pair potential and a model system of 256 particles. I investigated the influence of ${\mathrm{I}}^{-}$ ions on single-particle motion in the ${\mathrm{Ag}}^{+}$ subsystem. In addition, I showed that correlations between different ions must be distinctly reflected in frequency-dependent conductivity.

We have observed magnetic resonance in the ${}_{}{}^3{}_{}{}^{}T_{1\mathrm{u}}^{}{}_{}{}^{}$ excited levels of ${\mathrm{Ga}}^{+}$ in KBr using an optical detection technique. The $A_T$ and $A_X$ emissions take place from excited states which display tetragonal and trigonal symmetries respectively. A model assuming nearly equal linear coupling to $E_{\mathrm{g}}$ and $T_{2\mathrm{g}}$ modes and an additional bilinear coupling to totally symmetric modes, $A_{1\mathrm{g}}$, accounts for the available data: magnetic resonance spectra, and temperature and pressure dependence of the optical spectra.

We present the first pseudopotential calculation of the fundamental band gaps for heterostructures consisting of alternating monolayers of GaAs and ${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ ($0<~x<~1$). Significant differences are found between the GaAs-AlAs gaps and those of the ${\mathrm{Ga}}_{0.5}$${\mathrm{Al}}_{0.5}$As random alloy. The imaginary part of the dielectric function has been calculated for GaAs-AlAs and appears consistent with the experimentally reported optical absorption edge.

Observations by radiative detection of pulse magnetic resonance of oriented ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ nuclei in iron are reported. Multiple-pulse techniques are used to observe free-induction decays and spin echoes.