We report here the pressure-volume isotherm and x-ray-diffraction measurements for tert-butanol on graphite over the temperature range 220–250 K, with comparison to the other branched isomers of butanol. Unlike the other butanols, the first adsorbed layer of tert-butanol forms a bimolecular-layer-thick film and undergoes two first-order phase transitions with increasing vapor pressure. Analysis of the x-ray-diffraction pattern shows that the bimolecular adsorbed layer shares the same helical structure of hydrogen bonds as found in the bulk.

The exact quasiparticle renormalizaton is calculated for a localized hole in a quantum Heisenberg antiferromagnet. A bound magnon pole causes large increases in the quasiparticle renormalization. However, the renormalization remains finite.

${\mathit{D}}^{\mathrm{-}}$ centers have been unambigously identified in GaAs/(Ga,Al)As quantum wells by analysis of the dependence of the observed photoconductivity spectrum on the applied magnetic field and sample orientation. Theoretical investigations show that in magnetic fields of interest the ${\mathit{D}}^{\mathrm{-}}$ transitions do not involve photoionization of the centers as has been previously supposed but proceed from the ground state to discrete ${\mathit{p}}_{\mathrm{-}1}$- or ${\mathit{P}}_{+1\mathrm{}}$-like ${\mathit{D}}^{\mathrm{-}}$ levels, which lie above the N=0 and N=1 Landau-level energies, respectively. Tilting the sample leads to a predicted anticrossing of discrete ${\mathit{p}}_0$- and ${\mathit{p}}_{+1\mathrm{}}$-like ${\mathit{D}}^{\mathrm{-}}$ levels. Excellent agreement with experiment is obtained without any adjustable parameters.

The lattice model of a classical electron liquid with the Coulomb interaction and zero kinetic energy is considered. It is shown by both qualitative arguments and computer modeling that in this system the Coulomb gap exists near the chemical potential. Arguments are given that this is true for the nonideal quantum liquid as well. Nearest-neighbor hopping conductivity is studied at d=2. At low temperatures, the conductivity mechanism is shown to be a many-electron diffusion. At very small external disorder, the crossover from the diffusion to percolation has been found.

We study time-dependent Schrödinger operators in Aharonov-Bohm geometries where the flux threading the hole increases linearly with time. We show that the quasienergy operator has, in these cases, the same spectrum as the time-independent Stark Hamiltonian on the universal covering space. Combining known results on Stark Hamiltonians with a theorem of Bellissard, we prove that the energy of a particle on a finite ring, with smooth background potential, increases without bound as t→∞.

We directly observe the electromagnetic radiation emitted by electrons coherently oscillating between the two wells of a semiconductor coupled-quantum-well structure. Using time-resolved coherent detection of the submillimeter-wave radiation from these spatial charge oscillations, we trace up to fourteen oscillations at 1.5 THz before phase relaxation destroys the coherence of the oscillating wave packet. In addition to the oscillatory electromagnetic signal, we also observe an instantaneous signal from electric-field-induced optical rectification in the semiconductor structure.

The radiofrequency penetration depth λ(H,T) of the organic superconductor (BEDT-TTF${)}_2$Cu(NCS${)}_2$ was studied in the mixed state at moderate fields. The data can be scaled into a single functional form Δλ(H,T)=Δ${\lambda }^{\mathrm{*}}$(T)f(H/${\mathit{H}}^{\mathrm{*}}$(T)), where ${\mathit{H}}^{\mathrm{*}}$(T)×(1-t${)}^{3/2}$/t can be identified with a ‘‘depinning’’ or ‘‘irreversibility’’ line. We show that the scaling features are contained in a theory of vortex motion in a periodic pootential under the influence of thermal fluctuations, which describes the functional form quantitatively. The data for Δλ(H=0, T) are governed by the same (vortex) length scale as the finite-field data, suggesting that the zero-field state is not a conventional Meissner state obeying a London relation.

Unusual temperature dependence of electrical resistance has been observed in ultrathin superconducting films of Pb, Al, and Bi. In small magnetic fields, at low temperatures, sheet resistances varied with temperature as R≊${\mathit{R}}_0$ exp(T/${\mathit{T}}_0$), where ${\mathit{T}}_0$ and ${\mathit{R}}_0$ are constants. This result is not expected in conventional models of vortex motion involving thermal activation. On the other hand, it may be explained in a quantum tunneling picture.

Long-range antiferromagnetic order of the Sm ions in ${\mathrm{Sm}}_2$${\mathrm{CuO}}_4$ is observed via neutron diffraction at ${\mathit{T}}_{\mathit{N}}$=5.95 K. The magnetic structure consists of ferromagnetic sheets within the a-b planes, with the spins in alternate sheets aligned antiparallel. This spin structure and spin direction are completely different from those observed in any other copper-oxide superconductor system. The temperature dependence of the upper critical field ${\mathit{H}}_{\mathit{c}2}$ for the superconductor ${\mathrm{Sm}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_4$ (${\mathit{T}}_{\mathit{c}}$=23.5 K) shows a sudden increase in ${\mathit{H}}_{\mathit{c}2}$ at T/${\mathit{T}}_{\mathit{c}}$∼0.7, but this anomaly cannot be attributed to the Sm magnetic ordering. No anomaly in ${\mathit{H}}_{\mathit{c}2}$ is observed at the ${\mathit{T}}_{\mathit{N}}$ for Sm.

Optical phonons in metallic high-pressure phases of Si and Ge were studied up to 50 GPa by Raman scattering. Two Raman bands (LO, TO) were observed in the β-tin phase, one of which (LO) becomes soft on approaching the transition to primitive hexagonal. For hcp-Si there is one Raman-active mode (TO), and an additional mode is observed in the stability field of Si-VI. The available theoretical results agree within (10–20)% with the experimental results.

We report on the formation by mechanical alloying of fcc solid solution of Fe and Cu, which are immiscible. Intense codeformation of Cu with Fe and other high-melting bcc metals generates small fragments with tip radii of the order 1 nm such that capillary pressures force the atoms on these fragments to dissolve. The critical radius for dissolution is found to increase with solute content inside the spinodal thus leading to full dissolution of one of the components. The fcc-FeCu solid solutions have Curie temperatures similar to those of vapor-deposited alloys and a positive heat of mixing that is in accord with theoretical results.

We report transient light-scattering measurements upon the cessation of shear for a semidilute polymer solution under theta conditions. The polymer solution demonstrates two modes of relaxation for concentration fluctuations in equilibrium. The transient measurements show that the mechanism that couples the concentration fluctuations to the shear flow, and thereby enhances concentration fluctuations, selectively enhances only the slower of the two equilibrium modes. This selective enhancement generates a long-wavelength peak in the shear-enhanced structure.

An investigation of solutions by high-resolution x-ray fluorescence spectroscopy has been performed on chloride and sulfide solutions. In this study, dramatic Cl $K\beta$ and $K\alpha$ spectral changes are observed when NaCl(s) is dissolved in water. These spectral changes are interpreted on the basis of chemically dependent x-ray shakeoff satellites. Aqueous sulfide measurements were also performed indicating that, in contrast to Cl, a S-H $\sigma$ bond was observed about 3.5 eV below the S lone pair peak.

The Ta ${\mathit{N}}_7$-VV Auger spectrum of TaC(111) has been measured in coincidence with photoemission from the bulk and surface shifted Ta 4${\mathit{f}}_{7/2}$ core levels. Good agreement is found between the surface Auger spectrum and a self-convolution of the density of states (SCDOS) at surface Ta sites determined by a first-principles calculation. The bulk spectrum disagrees with the bulk SCDOS but is well described by an incoherent sum of the bulk SCDOS and the surface spectrum. A novel off-site Auger decay mechanism, first observed on Ta(100), accounts for these observations.

A cycle expansion for the Lyapunov exponent of a product of random matrices is derived. The formula is nonperturbative and numerically effective, which allows the Lyapunov exponent to be computed to high accuracy. In particular, the free energy and heat capacity are computed for the one-dimensional Ising model with quenched disorder. The formula is derived by using a Bernoulli dynamical system to mimic the randomness.

The Einstein theory of gravitation breaks down at very high curvatures. We propose a modification of the theory at Planck curvatures for which all isotropic cosmological solutions (even including matter) are nonsingular. All solutions asymptotically approach de Sitter space, a solution with limiting curvature.

Relativistic stellar oscillations are fluid and metric perturbations characterized by complex frequencies called quasinormal modes. This Letter presents a model which clarifies the extent to which such modes can be complete, in the sense of normal modes. It is found, for a specific class of Cauchy data, that, describing purely outgoing radiation, an expansion of the dynamics in terms of quasinormal modes can be constructed. For more general Cauchy data, it is shown that no useful distinction is possible between data that do and do not stimulate quasinormal oscillations.

We show that the Weinberg-Salam model has vortex solutions similar to semilocal strings for all values of the parameters. The stability of the solutions under small perturbations will depend on the parameters of the theory and, in particular, on the ratio of the Higgs boson mass to the Z boson mass.

A simple model is constructed which satisfies all the laboratory, astrophysical, and cosmological constraints discussed recently by Caldwell and Langacker for the possible existence of a 17-keV neutrino. It is mainly ${\nu }_{\mathrm{\tau }}$, with ν${\mathrm{¯}}_{\mathrm{\mu }}$ as its pseudo-Dirac partner, whereas ${\nu }_{\mathit{e}}$ is mainly a light pseudo-Dirac neutrino with an inert partner. The decay lifetime of the 17-keV neutrino is estimated to be 10 s or longer.

The fermion masses and mixings are derived from a small number of input parameters. The resulting six predictions are consistent with data and have interesting consequences for future experiments. The top quark is heavy, near 188 GeV; its precise mass is sensitive to ${\mathit{V}}_{\mathrm{cb}}$.