We have made a stringent test of time-reversal symmetry using nuclear-spin resonance in a rotationally cold, supersonic beam of thallium fluoride molecules. We searched for a shift of the 120-kHz thallium spin resonance when a 29.5 kV/cm external electric field was reversed relative to the nuclear spin and found this to be (1.4±2.4)×${10}^{\mathrm{-}4}$ Hz. This is a tenfold improvement over our previous measurement in thallium fluoride. The derived constraints on the proton and electron electric dipole moments and on T violation in both strong and weak interactions are correspondingly improved.

We consider the kinetics of a steady-state aggregation process in which the basic dynamical variable is a ‘‘charge’’ which can assume both positive and negative values. We rigorously show that the charge distribution follows a power law in the steady state which is sustained by random injection. The exponent of the power law depends both on the type of injection and on the spatial dimension.

Using a simple one-dimensional model, we show that the existence of the energy gap for excitations in an isotropic BCS superfluid leads to strongly nonlinear mechanical behavior of the liquid in the ballistic quasiparticle limit. The nonlinear damping of a vibrating wire in ${}_{}{}^3{}_{}{}^{}\mathit{B}$ below 200 μK is explained, both in its velocity dependence and magnitude. At modest velocities (υ>kT/${\mathrm{p}}_{\mathrm{F}}$), the damping force on an object moving through the superfluid becomes independent of velocity, an unexpected result with several interesting implications.

Nuclear-magnetic-resonance measurements of the magnetization of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ on thin ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixture films show discrete structure as a function of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ coverage over the range 0.0055≤$d_3$≤4 layers at a ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ coverage of 44 μmol/${\mathrm{m}}^2$ for 30≤T≤250 mK in a weakly polarizing 2-T field. A steplike doubling of the magnetization at $d_3$≊0.8 layers and a second less pronounced step at $d_3$≊1.5 layers are ascribed to the population of higher energy levels which evolve as the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ thickens. The magnetization as a function of temperature near the first step is fit by a two-level model with an energy gap $e_{12}$≊1.8 K at the step.

We report conclusive evidence for the existence of molecular local ordering in four phosphorus-selenium glasses. The compositions were chosen to span the P-rich glass-forming region and were ${\mathrm{P}}_2$Se, ${\mathrm{P}}_3$Se, ${\mathrm{P}}_4$Se, and ${\mathrm{P}}_{0.84}$${\mathrm{Se}}_{0.16}$. Raman spectra show unequivocally the existence in each glass of well-defined ${\mathrm{P}}_4$${\mathrm{Se}}_3$ cage molecules. All nine Raman-active internal modes of this molecule have been observed, with a clear trend of reduction of their intensity as the P content is increased. We find that these materials behave as a matrix-supported assembly of ${\mathrm{P}}_4$${\mathrm{Se}}_3$ molecules.

We have investigated the structural transition of the Pt(110)1×2 reconstruction using x-ray diffraction. We find weakening and broadening of the half-order peak with temperature above ${\mathrm{T}}_{\mathrm{c}}$=1080 K, exactly analogous to the Au(110)1×2 surface studied by LEED. Unlike the Au(110) result, however, we find the peak shifts as well, indicating that steps spontaneously appear in Pt(110) above ${\mathrm{T}}_{\mathrm{c}}$. Even though we find good agreement with theoretical 2D Ising exponents, the steps refute classification of this system as a simple two-state model, and favor a roughening description instead.

Novel deuteron multiple spin echoes are observed from HD and o-${\mathrm{D}}_2$ molecules trapped in hydrogenated amorphous silicon samples. The echo locations result from the combined action of intramolecular quadrupole and dipole couplings. Using molecular-beam values of the interactions, the observed echo times are predicted to within a few percent. For o-${\mathrm{D}}_2$, the echoes demonstrate mixing of I=0 and I=2, m=0 states. The existence of the HD and o-${\mathrm{D}}_2$ echoes at low temperatures requires crystal-field admixture of higher J states into the rotational ground state of the molecules.

The electronic structure near (111) twin stacking faults in Cu, Ir, and Al is investigated with the recently developed layer Koringa-Kohn-Rostoker method. The calculated stacking-fault energies are 341 mJ/${\mathrm{m}}^2$ (Ir), 118 mJ/${\mathrm{m}}^2$ (Al), and 58 mJ/${\mathrm{m}}^2$ (Cu), in excellent agreement with experiment. These trends are discussed in terms of changes in local bonding and symmetry at the stacking fault.

We report here the measurements of the energy and dispersion of the surface plasmons on Ag single crystals in UHV using angle-resolved electron-energy-loss spectroscopy. The energy of small-momentum surface plasmons depends upon crystal face and, for Ag(110), upon crystal orientation. The differences in the energies of the surface plasmons, which cannot be explained by a jellium model, are discussed in terms of the contributions to the dielectric response from surface states and truncated bulk band states.

By applying the perturbed-γ-ray-distribution method following heavy-ion reactions we have observed strong magnetic moments for isolated Fe ions in solid and liquid Hg reflecting a Curie-type local susceptibility along with a small Fe spin-fluctuation rate. The magnetism of Fe ions in Hg exhibits qualitative differences to the behavior of Fe in sp band metal hosts but is strikingly similar to the magnetism of Fe in hosts with d- band electrons, including Cu, Ag, and Au. We propose that the interaction of Fe 3d with Hg 5d band electrons is crucial for the existence and stability of Fe moments in Hg.

The intra-Landau-band magnetoplasma spectrum of a periodically density-modulated two-dimensional electron gas is shown to exhibit unusual oscillatory behavior. Such oscillations (periodic in 1/B) are seen to arise from the commensurability of the spatial period of the modulation with the cyclotron-orbit size at the Fermi level.

We use weak-coupling methods to calculate the effective interaction between quasiparticles induced by charge and spin fluctuations in a three-band model for the copper-oxide superconductors with both intersite and intrasite repulsion. The instabilities to superconducting states of different symmetries are calculated; besides the d-wave superconductivity near the antiferromagnetic instability, we find that extended s-wave superconductivity is favored by a charge transfer resonance close to a valence instability. A phase diagram similar to experiments is obtained.

Neutron scattering has been used to study the magnetic order of the Er ions in superconducting ${\mathrm{ErBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$. Above the 3D Néel temperature (${\mathrm{T}}_{\mathrm{N}}$=0.618 K) a rod of scattering characteristic of 2D behavior is unambiguously observed, showing that the magnetic interactions of the rare-earth ions are highly anisotropic; below ${\mathrm{T}}_{\mathrm{N}}$ the order parameter follows the exact Onsager solution for a 2D Ising antiferromagnet. At low T, two separate types of simple 3D antiferromagnetic structures are found, one characterized by a wave vector of (1/2,0,0), and the other by (1/2,0,1/2).

A burst of ${\nu }_{\mathrm{e}}$ radiated when the hydrodynamic shock formed in a core-bounce supernova breaks out of the neutrinosphere can preheat the matter and dissociate nuclei ahead of the shock. The extent of this is calculated self-consistently with nuclear statistical equilibrium using the heating rates on nucleons and nuclei including the giant resonance transitions. The predissociation can be substantial if the effective temperature of the neutrino burst is moderately large, thus contributing towards shock survival and prompt supernova explosion.

Particles of several TeV that remain from the Big Bang could comprise the cosmic closure density and, if unstable at the grand unification scale, they could provide the observed anomalous positron component in the cosmic radiation at 10–20 GeV. The model predicts a diffuse γ-ray signal that should stand out above the expected background above 10 GeV.

We show that the supersymmetry algebra for supersymmetric extended objects can contain, depending on the topology of space, topological charges, the origin of which is the Wess-Zumino term in the effective action. We exhibit the consequences of these charges for the phenomenon of partial breaking of supersymmetry.

We have searched for events with new-particle topologies in 390 hadronic Z decays with the Mark II detector at the SLAC Linear Collider. We place 95%-confidence-level lower limits of 40.7 GeV/$c^2$ for the top-quark mass, 42.0 GeV/$c^2$ for the mass of a fourth-generation charge -(1/3 quark, and 41.3 GeV/$c^2$ for the mass of an unstable Dirac neutral lepton.

A stochastic macroscopic approach to giant dipole resonances (GDR’s) in hot rotating nuclei is presented. In the adiabatic limit the theory reduces exactly to a previous adiabatic model where the unitary invariant metric is used to calculate equilibrium averages. Nonadiabatic effects cause changes in the GDR cross section and motional narrowing. Comparisons with experiments where deviations from the adiabatic limit are substantial are shown and can be used to determine the damping of the quadrupole motion at finite temperature.

Spin-spin cross sections of ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ have been measured for neutrons between 20 and 50 MeV with high precision. Absolute size and energy dependence of the data agree well with existing predictions from folding model calculations. The data can also be reproduced with phenomenological spin-spin potentials, but do not allow to distinguish between spherical and tensor interactions. The deduced spin-spin strengths are close to 1 MeV.

Using synchrotron radiation, we have investigated, over an extended photon energy range, the full photoelectron spectrum following ionization in the 2p subshell of Na atoms laser excited into the 2${\mathit{p}}^6$3${\mathit{p}}^2$${\mathit{P}}_{3/2}$ state. We have determined the relative cross sections for leaving the positive ions in various final states, corresponding to the main line and the satellite lines. In particular, we have observed a strong enhancement of the relative intensity of the shakeup satellites in the excited atom. Our measurements allow testing of the validity of a many-body calculation of the 2p-photoionization cross section.