We study the zero-temperature electron plasma in a strong magnetic field in the Hartree-Fock approximation. The calculations are based on an expression for the density matrix which allows all Coulomb integrals to be performed explicitly and allows exchange to be treated exactly. We find that the ground state changes from a charge-density-wave state with Q parallel to the field, to a uniform-density state, then to a crystal state in the holes of the lowest Landau level, and finally to an electron-crystal state as the magnetic field is increased.

We have used surface extended x-ray absorption fine structure (SEXAFS) to study the local geometry around barium atoms on thermionic cathodes. On the surfaces of tungsten and tungsten-osmium alloy dispenser cathodes Ba is bonded to oxygen with a well-defined short-range order. The Ba-O distance is similar (2.62±0.04 Å) for the two cathodes, with oxygen atoms occupying hollow sites of the substrate. However, the alloy cathode has Ba bonded to two oxygen near neighbors (compared to one for the tungsten cathode), which will enhance the surface dipole, thus explaining the observed lower work function.

Supercomputer simulations of the elementary A+B→0, diffusion-limited reaction were performed under steady-source conditions, on a cubic and a fractal lattice. While both reaction orders have the classical value (X=2) a dramatic segregation (‘‘morphogenesis’’) appears for the Sierpiński gasket ‘‘lattice.’’ This is relevant to chemical reactions on heterogeneous catalysts, to annealing of radiation damage and electron-hole recombination in inhomogeneous media, to charge polarization in clouds, and to possible matter-antimatter distributions in a steady-state universe.

The quantum energy eigenvalues near the separatrix energy are found by combination of previous analysis of the quantum states near a barrier top with recent results for the behavior of the classical action near a separatrix. It is found that the minimum energy separation vanishes only logarithmically with Planck’s constant. As a result, quantum aspects of the states of a Penning trap should be observable.

The problem of gauge and parametrization dependence in self-consistent dimensional reduction of five-dimensional quantum gravity is discussed. It is shown how the modification of the background-field method suggested by Vilkovisky is crucial for obtaining the correct result. We find that there are no physically acceptable self-consistent solutions of the form ${\mathrm{R}}^4$×${\mathrm{S}}^1$ at the one-loop level.

We present a numerical study of stochastic differential equations using the XY model in two dimensions as an example. ‘‘Accelerated’’ and ‘‘hybrid’’ algorithms have been implemented and show their advantages over more standard methods. The (partial) evasion of critical slowing down by accelerated algorithms is studied on a sequence of lattices ${16}^2$, ${32}^2$, and ${64}^2$..AE

We show that parton-parton scattering processes in QCD drive a rapid increase in the proton-proton scattering cross section at high energies, and use a diffraction-scattering formalism to obtain quantitative predictions for ${\sigma }_{\mathrm{tot}}$, ${\sigma }_{\mathrm{inel}}$, and ${\sigma }_{\mathrm{el}}$ at Superconducting Super Collider and cosmic-ray energies. We also predict a very rapid increase in the number of minijet events with √s .

We have investigated the transitions Υ(3S)→${\pi }^{+}$${\pi }^{\mathrm{-}}$Υ(1S) and Υ(3S)→${\pi }^{+}$${\pi }^{\mathrm{-}}$Υ(2S) and the cascade process Υ(3S)→Υ(2S)+X, Υ(2S)→${\pi }^{+}$${\pi }^{\mathrm{-}}$Υ(1S), both in the exclusive decay mode where the daughter Υ state decays into two leptons, and in the inclusive decay mode where the daughter Υ state decays hadronically. Results are presented on branching fractions and the properties of the ${\pi }^{+}$${\pi }^{\mathrm{-}}$ system. Possible evidence for the transition Υ(3S)→${\pi }^{+}$${\pi }^{\mathrm{-}}$Υ${(1\mathrm{}}^1$$P_1$) is presented.

We have used a silicon-microstrip vertex detector with Tagged Photon spectrometer to measure the lifetimes of charmed mesons produced by a high-energy photon beam at Fermilab. The $D^{+}$ lifetime, based on 969 $D^{+}$→$K^{\mathrm{-}}$${\pi }^{+}$${\pi }^{+}$ decays, is measured to be (1.06±0.05±0.03)×${10}^{\mathrm{-}12}$ s. Using 1360 $D^0$ decays into the modes $K^{\mathrm{-}}$${\pi }^{+}$ and $K^{\mathrm{-}}$${\pi }^{+}$${\pi }^{\mathrm{-}}$${\pi }^{+}$, we determine the lifetime to be (0.435±0.015±0.010)×${10}^{-12}$ s. The ratio τ($D^{+}$)/τ($D^0$) obtained from these two measurements is 2.44±0.14±0.08.

Using projection techniques, we show that stretching occurs in the sdg interacting-boson model (IBM) but not in the sd model. As a result the sdg IBM allows g-factor variations in the ground-state band in accordance with recent experiments, and as such may provide a signature for the g boson.

Nucleon-transfer cross sections have been measured at subbarrier energies in collisions between Sn target nuclei and light ${(}^{16}$,18O) and heavy ${(}^{58}$Ni) projectile nuclei. Large differences in cross sections correlate directly with the subbarrier fusion enhancement, suggesting nucleon transfer as an important doorway to fusion with a direct dependence on the overall transfer strengths. Simple two-level mixing considerations support this picture.

The angular distribution of alpha particles with respect to the spin direction of the residual nuclei is used to probe the shapes of the emitting systems. Two compound systems have been studied: ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ and ${}_{}{}^{110}{}_{}{}^{}\mathrm{Sn}$. Deformed emission shapes are required in order to understand the alpha-gamma correlations in the ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ system, but not for the ${}_{}{}^{110}{}_{}{}^{}\mathrm{Sn}$ compound system. These conclusions are identical to those reached by the study of giant resonances built on excited states for very similar systems.

From the analogy between the collective quadrupole decay among compound nuclear states in strongly rotating nuclei and the phenomenon of nuclear magnetic resonance, it is possible to formulate a model of nuclear rotational damping which exhibits interesting correspondences between nuclear and atomic statistical processes.

Muon-catalyzed deuterium-tritium fusion was investigated within a wide range of mixtures in liquid and gas (23–35 K) by detection of fusion neutrons. Our improved analysis includes hyperfine effects and allows a clear separation of intrinsic dt sticking ${\omega }_s$ from kinetic effects. Strongly density-dependent cycle rates with values up to 1.45×${10}^8$ ${\mathrm{s}}^{\mathrm{-}1}$, yields of 113 fusions per muon, and ${\omega }_s$=(0.45±0.05)% are found. In comparison with previous experiments we confirm that ${\omega }_s$ in liquid is lower than theoretically predicted, but do not find a strong dependence on either $c_t$ or density.

Experiments on photodetachment from selenium negative ions in magnetic fields of 6.33 and 7.83 T have allowed the observation of photodetachment from resolved Zeeman levels for the first time. The measured relative detachment strengths for the Zeeman thresholds are not in agreement with the presently available theoretical prediction. Some possible sources of this disagreement are suggested.

The first comparison of core-state populations of initially bare ${\mathrm{Kr}}^{36+}$ ions emerging from gaseous and solid targets is presented. Another new important feature of this experiment lies in the fact that for such fast heavy ions, the single-collision condition is fulfilled even in solid targets. Our results can be explained by a wake-field–induced Stark mixing of the substates in a solid. Further coherence angles and field strength measurement are discussed.

We have measured the K-shell ionization probability $P_K$ at 172° across the 10.00-MeV isobaric analog resonance in the reaction ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$(p,p${)\mathrm{}}^{138}$Ba. An excursion of more than 200% from the off-resonance $P_K$ value permits a sensitive comparison with recently calculated atomic-ionization amplitudes. The effects of nonresonant background nuclear scattering and compound-elastic nuclear scattering are considered. The experimental results are found to be consistent with a negligible compound-elastic contribution.

A method for continuous coherence transfer in magnetic resonance is proposed and demonstrated with real-time detection of a double-quantum NMR coherence. The technique, which has implications for a broad range of magnetic resonance experiments, is related to effects observed in the study of coherent optical transients.

We report the first direct observation of electron inelastic scattering from the pondermotive potential of an intense laser pulse in vacuum. Electrons gained up to 0.2 eV when scattered from the temporal leading edge of a 1064-nm (1.165 eV), 140-psec laser pulse, and lost comparable amounts of energy when scattered from the trailing edge. When directed to the most intense part of the pulse, they were deflected out of the beam.

The dynamics of the interaction of a single Rydberg atom with a single mode of an electromagnetic field in a superconducting cavity was investigated. Velocity-selected atoms were used and the evolution of the atomic inversion as atom and field exchange energy was observed. The quantum collapse and revival predicted by the Jaynes-Cummings model were demonstrated experimentally for the first time. The evaluation of the dynamic behavior of the atoms allows us to determine the statistics of the few photons in the cavity.