X-ray-scattering investigation of stoichiometric silver $\beta$-alumina reveals a clear phase transition between the high-temperature conducting-ions quasiliquid sublattice, and a lowtemperature crystalline state. Preliminary, structural analysis of the low-temperature crystalline order confirms the type of organization previously deduced for the low-temperature short-range order of nonstoichiometric silver $\beta$-alumina.

We report reversible hole burning in the inhomogeneously broadened zero-phonon line of ${F_3}^{+}$ in NaF at 5456 Å. The hole recovery time shows two components: 2.5 sec assigned to triplet-state relaxation and 70 min assigned to electron tunneling from an adjacent center. These holes were used to measure the homogeneous linewidth (17 MHz) and the linear Stark effect. We find the excited ${}_{}{}^1{}_{}{}^{}E$ level has a distribution of zero-field splittings inside the inhomogeneous lines, which quenches the first-order Zeeman effect.

The small-polaronic diffusion associated with simple models of light interstitials in bcc metals has been investigated. By transcending the simplifications which are often introduced in studying electronic small-polaron transport, we calculate diffusion coefficients which are reasonably consistent with available data. In particular, an explanation of the "anamalous" isotope dependence observed for hydrogen diffusion in bcc metals emerges from these studies.

Experimental evidence is presented for an electron-liquid to electron-crystal phase transition in a sheet of electrons on a liquid-He surface. The phase transition has been studied for electron areal densities from 3×${10}^8$ ${\mathrm{cm}}^{-2\mathrm{}}$ to 9×${10}^8$ ${\mathrm{cm}}^{-2\mathrm{}}$ and has yielded melting temperatures between 0.35 and 0.65 K. The phase transition occurs at $\Gamma =137\mathrm{}\pm 15$, where $\Gamma$ is a measure of the ratio of potential energy to kinetic energy per electron.

We analyze the vibrational modes of a two-dimensional electron solid, coupled to the ripplon modes of a liquid-helium surface, as a function of temperature and external electric pressing field. Resonance observed experimentally by Grimes and Adams are thereby explained.

We have identified occupied surface-state bands from angle-resolved photoelectron energy distribution curves of Au(112), Au(100), and Au(110), which are located in $\mathrm{sp}$ gaps of the projected bulk band structure. An approximate criterion for their possible experimental existence is given.

First-principles calculations of electronic energies of hydrogenated amorphous silicon have been performed for a series of realistic structural models in which hydrogen appears as SiH, Si${\mathrm{H}}_2$, Si${\mathrm{H}}_3$, ${\left(\mathrm{S}\mathrm{i}{\mathrm{H}}_2\right)}_2$, and SiHHSi (a broken Si-Si with two H atoms). Whereas all these models are consistent with photoemission experiment (less so for Si${\mathrm{H}}_3$), only the last two are found to give band-gap states. The broken-band model is in good agreement with several sets of experiments.

Muonium-spin-rotation experiments at low fields (<75) show evidence for the interaction of the interstitial charge distribution of crystalline quartz with the intrinsic electric quadrupole deformation of the triplet ground state of the muonium atom.

Studies on the effect of charged (Ti) and uncharaged (Ta) impurities on the non-Ohmic behavior of and microwave absorption in Nb${\mathrm{Se}}_3$ show that (1) the characteristic field $E_0$ increases as $c^2$ ($c=\mathrm{Ta}\mathrm{concentration}$), in agreement with a recent calculation by Lee and Rice; (2) the microwave absorption is suppressed by impurities; and (3) charged impurities are strikingly more effective in supressing the anomalous properties. These conclusions provide very strong evidence for Fröhlich sliding-mode conductivity in the nominally pure compound.

Infrared luminescence has been observed and the emission spectra in the 2.5-8.0-μm region determined for a silicon crystal exposed to Xe${\mathrm{F}}_2$ gas. In contrast to the broad and structureless emission in the uv and visible regions previously reported for some gassolid systems, the ir spectrum exhibits characteristic fine structure. Furthermore, the emitted radiation shows strong polarization and angular dependence indicating that the emitting species are on the crystal surface.

If scattering amplitudes are ordinary complex numbers (not quaternions) then there is a universal algebraic relationship between the six coherent cross sections of any three scatterers (taken singly and pairwise). A violation of this relationship would indicate either that scattering amplitudes are quaternions, or that the superposition principle fails. Some experimental tests are proposed, involving neutron diffraction by crystals made of three different isotopes, neutron interferometry, and $K_S$-meson regeneration.

Excitation functions for the dominant fusion channels in the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ reactions have been measured from 7 to 25 MeV (c.m.) using $\gamma$-ray spectroscopy. Comparison with the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ system shows that gross structure persists in the $\alpha$-out channel for ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ but is not apparent in this channel for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, although observed in the inelastic channels for the latter. ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ is the first system not comprised of $\alpha$-cluster nuclei to exhibit gross structures in fusion channels.

The second-order interaction potential has been calculated for two colliding nuclei where target excitation is induced by the interaction between a nucleon and the incoming self-consistent one-body field of the projectile. The real part of the second-order term is insignificant for distances larger than the touching radius, but significant for smaller distances. The imaginary potential agrees favorably with phenomenological results.

Time-dependent Hartree-Fock-Bogoliubov calculations in three dimensions are reported for the fusion of two ${}_{}{}^{118}{}_{}{}^{}\mathrm{Pd}$ isotopes and subsequent fission of the compound nucleus ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$. Constant-strength pairing, and simplified Skyrme plus Yukama and Coulomb interactions were included. A new result is the appearance of (nonaxial) surface oscillations in the compound or fissioning systems.

The first three moments of the $\gamma$-ray multiplicity distribution and the out-of-plane $\gamma$-ray anisotropy have been measured simultaneously as a function of mass asymmetry for the strongly damped products of the reaction ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$ with 168-MeV ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. The large variance of the multiplicity appears to be associated with the small anisotropy. These results indicate a random component of angular momentum which is comparable to the aligned component induced by tangential friction.

Observations are reported from the first systematic studies of proton radiative capture at intermediate energies. In addition to captures to the ground and first few excited states, the reactions ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$($p$,$\gamma$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$($p$,$\gamma$)${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ reveal unexpectedly strong transitions to isolated high-lying states. These latter transitions could take place via "second-harmonic" giant resonances. Protons on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ produce a rich spectrum of $\gamma$ rays which may arise from captures to high-lying single-particle states.

We discuss a close connection between the formula of Banks, Bender, and Wu for the asymptotics of the Rayleigh-Schrödinger coefficients of the two-dimensional rotationally symmetric anharmonic oscillator and the behavior of resonances of the hydrogen Stark problem in two regimes: small field (Oppenheimer's formula) and large field (where we obtain the new results $\arg E\to -\frac{\pi }{3}$, $\mathrm{}\left|E\right|\mathrm{}\sim \alpha {\left[F\right(\ln F\left)\right]}^{\frac{2}{3}}$ for $F$, the electric field strength, going to infinity). We also announce a rigorous proof of Bender-Wu-type formulas.

The collisionless drift wave and drift-Alfvén wave instabilities in a sheared magnetic field are considered using the complex transformation technique of Antonsen. It is shown that no unstable bounded eigensolutions for the finite-$\beta$ radial eigenmode equations exist. We also present a more general technique based on the wave-flux conservation and find, furthermore, that the convective amplification of drift waves in the electrostatic limit can be anomalously large, which could lead to enhanced transport in tokamaks.

A fully ionized plasma column was heated with a relativistic electron beam. Experiments in which plasma heating was dominated by the beam-plasma two-stream interaction demonstrated a scaling of energy deposition with the beam-to-plasma density ratio and the beam angular scatter in accordance with a theorectial model of the two-stream instability. Beam-to-plasma energy-transfer efficiencies exceeding 25% and plasma electron temperatures of 600 eV were observed.

Contrary to expectation, droplets did not nucleate in the critical fluid of isobutene. Droplets formed only at $\frac{T}{T_c}<~0.96$, where $\frac{n}{n_c}<~0.38$. In low-density vapor, droplet formation began at a temperature greater than the coexistence temperature at that density. The magnitude of the gap ($T_{\mathrm{onset}}-T_{\mathrm{coexist}}$) correlated with the surface tension of the liquid at $T_{\mathrm{onset}}$. Average droplets in the coexistence vapor contained 730 000 molecules at 297 K and 2000 molecules at 397 K.