We report the first observation of an ultraviolet emission continuum attributed to transitions originating in bound Rydberg states of ${\mathrm{H}}_3$ and terminating on the repulsive ground state.

We have observed 6snd ${\mathrm{}}^1$${\mathrm{D}}_2$ Rydberg states of Ba with principal quantum numbers up to n=290. To our knowledge these are the largest atoms which have been produced under laboratory conditions up to now. Rydberg atoms with n=78 were subject to small electric (F≲1 V/cm) and magnetic (H≲850 G) fields to produce highly resolved spectra of Stark and diamagnetic manifolds. Due to interference effects caused by the presence of nonhydrogenic states within the manifolds the distribution of oscillator strength varies dramatically and was found to be strikingly similar for Stark and diamagnetic manifolds.

We have measured the heliumlike titanium emission lines produced during electron-cyclotron heating (ECH) of Doublet III tokamak plasmas. The spectra observed during ECH at a level of 1 MW show considerable departure from those of ohmically heated plasmas. Theoretical analysis of line intensities shows that the ECH plasma is in disequilibrium with a net state of ionization and relatively little recombination. A departure from the Maxwellian electron distribution is inferred. Electron temperatures deduced from ratios of dielectronic recombination lines to the resonance line (i.e., $d_{13}$/w, k/w, and j/w) are in significant disagreement with temperatures measured by the Thomson scattering system.

Symmetric in-plane and extremely asymmetric out-of-plane Ne-diffraction rainbows obtained from Ni(113) along [332¯] show that the close-packed (111) facets are more strongly corrugated than the more open (100) ones, in surprising contrast to expectation. Surface-charge-density calculations with overlapping atomic densities indicate that surface bonding causes appreciable electronic charge flow from the (111) to the (100) facets, filling up the fourfold hollows completely.

Charge-density waves on cleaved surfaces of 1T-${\mathrm{TaS}}_2$ appeared at 77 K as hexagonal arrays of mounds with spacings of (3.5±0.3)${\mathrm{a}}_0$, where ${\mathrm{a}}_0$=3.346 Å is the lattice spacing of the 1T-${\mathrm{TaS}}_2$. In contrast, cleaved surfaces of 2H-${\mathrm{TaSe}}_2$ at 77 K showed only atoms. The tunneling microscope was operated under liquid nitrogen with a ${\mathrm{Pt}}_{0.8}$${\mathrm{Ir}}_{0.2}$ tip for both types of samples.

A semiempirical model for the dynamical structure factor, S(Q,ω), in a simple liquid is presented. This is a modification of the Lorentzian form predicted by linear hydrodynamics that enable it to be extended into the viscoelastic region while still retaining finite moments. The model leads directly to a criterion for the existence of a sound mode which includes the possibility of soft modes and dispersion gaps. By a suitable choice of parameters the experimental results for liquid Ar and molten Rb may be explained.

A three-dimensional analysis of the electrohydrodynamic instability in a planar-oriented nematic liquid crystal with stress-free boundary conditions shows that for appropriate, realistic parameters of materials like MBBA and PAA the instability sets in for a periodic roll structure that is oblique with respect to the undisturbed director nbhat. By a change in the frequency and/or application of a magnetic field a continuous transition from perpendicular to oblique rolls can be induced. We analyze the mechanism, discuss the possible influence of nonlinearities, and compare with experiments.

A density matrix formulation of the dynamical theory of spectral shifts from correlated lattice vibrations in electron channeled radiation is presented. For lower-energy channeling, in which two bound levels exist in the channeling potential, positive shifts can be demonstrated. In the case of higher-energy channeling, where the number of bound levels increases, reduced positive shifts and negative shifts are shown. The theory suggests a novel method for experimentally determining a transverse, vibration correlation length in crystals.

Iron pentacarbonyl has been thermally decomposed in an organic liquid. Mössbauer spectroscopy and x-ray diffraction studies show that the sample contains small particles of a metallic glass. Annealing of the particles at 523 K results in crystallization of the particles into a mixture of α-Fe and χ-${\mathrm{Fe}}_5$${\mathrm{C}}_2$. The mechanism of glass formation is discussed.

We show that the large anomalous Hall constants of mixed-valence and Kondo-lattice systems can be understood in terms of a simple resonant-level Fermi-liquid model. Splitting of a narrow, orbitally unquenched, spin-orbit split, f resonance in a magnetic field leads to strong skew scattering of band electrons. We interpret both the anomalous signs and the strong temperature dependence of Hall mobilities in ${\mathrm{CeCu}}_2$${\mathrm{Si}}_2$, ${\mathrm{SmB}}_6$, and ${\mathrm{CePd}}_3$ in terms of this theory.

A new theory is presented for describing band gaps and electronic structures of transition-metal compounds. A theoretical phase diagram is presented in which both the metallic sulfides and insulating oxides and halides occur in a quite natural manner.

Using a new technique, we measure the energy-loss lifetime for electrons in a metal from 25 to 320 mK. Applying a small electric field, of order 1 μV/cm at 25 mK, causes carriers to heat above the temperature of the phonon bath. The temperature difference induced reflects the rate of energy transport between the electrons and lattice. The 1-ms energy-loss lifetime and 1-cm inelastic diffusion length we have measured at 25 mK are the largest ever obtained.

Lattice vibrations of the high-${\mathrm{T}}_{\mathrm{c}}$ superconductor ${\mathrm{BaPb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Bi}}_{\mathrm{x}}$${\mathrm{O}}_3$ are investigated by Raman scattering. The breathing mode of ${\mathrm{BiO}}_6$ octahedra is assigned to the 569 ${\mathrm{cm}}^{\mathrm{-}1}$ peak which has large scattering intensity in ${\mathrm{BaBiO}}_3$. The temperature-dependent soft modes at 121 ${\mathrm{cm}}^{\mathrm{-}1}$ in ${\mathrm{BaPb}}_{0.7}$${\mathrm{Bi}}_{0.3}$${\mathrm{O}}_3$ and 48 ${\mathrm{cm}}^{\mathrm{-}1}$ in ${\mathrm{BaBiO}}_3$ are assigned to the rotational modes of Pb(Bi)${\mathrm{O}}_6$. A remarkable correlation is found between ${\mathrm{T}}_{\mathrm{c}}$ and the scattering intensity of the 43- and 100-${\mathrm{cm}}^{\mathrm{-}1}$ peaks. The origin of these modes is discussed.

We show that localization effects can be significantly enhanced in the presence of quantum size effects. We have made measurements on single-crystal gold films of thicknesses less than 10 nm. An enhanced logarithmic temperature dependence of the resistance and a negative magnetoresistance provide qualitative support for this model.

We derive the dispersion relation for a new gapless Goldstone mode in the fractional quantum Hall effect of a multicomponent electron gas. We expect these modes to be important for some of the observed filling factors (e.g., ν=(1/3)) in multivalley semiconductors.

New numerical results from simulations of cosmological gravitational clustering are displayed. They show a saturation of the nonlinear modes which can be predicted by a quasilinear-type theory. However, such a theory is shown to be inadequate for describing the short-range correlations of galaxies. First nonlinear contributions are computed. Contrary to earlier claims, a nonlinear energy transfer does not shorten the collapse time in the adiabatic scenario.

Field contributions and the Gauss theorem for retarded functions lead to a new formula for gravitational radiation energy loss. It clarifies the applicability of the quadrupole formula for systems with ${\mathrm{T}}^{\mathrm{ik}}$-dominated motion. Applied to the axially symmetric two-body problem with equation of state ε=ε(P) for short free-fall times, the new formula yields the bulk-motion quadrupole-formula result. This contrasts our earlier larger flux with unconventional equation of state and that of critics claiming a quadrupole formula flux from internal motions. An order of magnitude estimate yields potential corrections of quadrupole formula size after ∼${10}^2$ yr for the binary pulsar.

We construct the evolution operator U of the quantum Chirikov map explicitly. When 2πħ=M/N is a rational number, corresponding to the quantum resonance condition of Casati et al., we can reduce the operator U as a direct sum of independent N×N unitary matrices. We then obtain numerically the eigenstates of the same system. We describe these eigenstates in the coherent-state representation and find that they follow closely the Kolmogorov-Arnol’d-Moser curves and other classical orbits. We discuss the long-time behavior of initially localized quantum states.

Using Monte Carlo methods, we conclude that there are no first-order phase transitions in SU(5) lattice gauge theory with a renormalization-group–improved action, the form of which has been proposed previously by a block-spin renormalization-group analysis. This is quite different from the situation with the standard one-plaquette action.

We propose a renormalization method based on a unitary transformation and apply this to the problem of $g$-boson effects in the interacting-boson model.