We use Lloyd’s mirror to modulate electron photoemission in photoemission electron microscopy. This results in the projection of Lloyd’s fringes on to three-dimensional (3D) surface objects. An iterative reconstruction method is used to correct for distortions in the fringe pattern due to the cathode immersion lens, thereby providing a quantitative interpretation of surface shape. It is therefore possible to extract 3D height information directly from a two-dimensional, plan-view image. The technique is of sufficient intensity and contrast to study real-time changes in surface topography and we apply the method to study unusual contact-line dynamics during the reactive wetting of metal droplets.

We present a novel approach to surface chemistry studies using scanning tunneling microscopy (STM), where dissociation of molecules adsorbed on metal surfaces is induced nonlocally in a 10–100 nm radius around the STM tip by hot electrons that originate from the STM tip and transport on the surface. Nonlocal molecular excitation eliminates the influence of the STM tip on the outcome of the electron-induced chemical reaction. The spatial attenuation of the nonlocal reaction is used as a direct measure of hot-electron transport on the surface.

We analyze the structure of Haliotis rufescens nacre, or mother-of-pearl, using synchrotron spectromicroscopy and x-ray absorption near-edge structure spectroscopy. We observe imaging contrast between adjacent individual nacre tablets, arising because different tablets have different crystal orientations with respect to the radiation’s polarization vector. Comparing previous data and our new data with models for columnar nacre growth, we find the data are most consistent with a model in which nacre tablets are nucleated by randomly distributed sites in the organic matrix layers.

We explore the limits of liquid pumping by “classical propellers” with molecular-scale blades. Our molecular dynamics simulations reveal a huge sensitivity of pumping to the chemistry of the blade-liquid interface. We demonstrate selective pumping of hydrophobic and hydrophilic liquids, where the pumping rate is determined by the effective profile of the solvated nanoscopic blades. These results have important implications for a potential design and assembly of molecular pumps and motile devices.

In antenna theory, antenna parameters are directly related to the wavelength $\lambda$ of incident radiation, but this scaling fails at optical frequencies where metals behave as strongly coupled plasmas. In this Letter we show that antenna designs can be transferred to the optical frequency regime by replacing $\lambda$ by a linearly scaled effective wavelength ${\lambda }_{\mathrm{eff}}=n_1+n_2\lambda /{\lambda }_p$, with ${\lambda }_p$ being the plasma wavelength and $n_1$, $n_2$ being coefficients that depend on geometry and material properties. It is assumed that the antenna is made of linear segments with radii $R\ll \lambda$. Optical antennas hold great promise for increasing the efficiency of photovoltaics, light-emitting devices, and optical sensors.

We propose a model for $1/f$ flux noise in superconducting devices ($f$ is frequency). The noise is generated by the magnetic moments of electrons in defect states which they occupy for a wide distribution of times before escaping. A trapped electron occupies one of the two Kramers-degenerate ground states, between which the transition rate is negligible at low temperature. As a result, the magnetic moment orientation is locked. Simulations of the noise produced by randomly oriented defects with a density of $5\times {10}^{17}{\mathrm{m}}^{-2}$ yield $1/f$ noise magnitudes in good agreement with experiments.

We present a method of simulating the Dirac equation in $3+1$ dimensions for a free spin-$1/2$ particle in a single trapped ion. The Dirac bispinor is represented by four ionic internal states, and position and momentum of the Dirac particle are associated with the respective ionic variables. We show also how to simulate the simplified $1+1$ case, requiring the manipulation of only two internal levels and one motional degree of freedom. Moreover, we study relevant quantum-relativistic effects, like the Zitterbewegung and Klein’s paradox, the transition from massless to massive fermions, and the relativistic and nonrelativistic limits, via the tuning of controllable experimental parameters.

Electromagnetically induced transparency is predicted for x rays in laser-dressed neon gas. The x-ray photoabsorption cross section and polarizability near the Ne $K$ edge are calculated using an ab initio theory suitable for optical strong-field problems. The laser wavelength is tuned close to the transition between $1s^{-1}3s$ and $1s^{-1}3p$ ($\sim 800\mathrm{nm}$). The minimum laser intensity required to observe electromagnetically induced transparency is of the order of ${10}^{12}\mathrm{W}/{\mathrm{cm}}^2$. The ab initio results are discussed in terms of an exactly solvable three-level model. This work opens new opportunities for research with ultrafast x-ray sources.

Sputtering of an amorphous or crystalline material by an ion beam often results in the formation of periodic nanoscale ripple patterns on the surface. In this Letter, we show that, in the case of alloy surfaces, the differences in the sputter yields and surface diffusivities of the alloy components will also lead to spontaneous modulations in composition that can be in or out of phase with the ripple topography. The degree of this kinetic alloy decomposition can be altered by varying the flux of the ion beam. In the high-temperature and low-flux regime, the degree of decomposition scales linearly with the ion flux, but it scales inversely with the ion flux in the low-temperature, high-flux regime.

We uncover a new pathway towards multiferroicity, showing how magnetism can drive ferroelectricity without relying on inversion symmetry breaking of the magnetic ordering. Our free-energy analysis demonstrates that any commensurate spin-density-wave ordering with a phase dislocation, even if it is collinear, gives rise to an electric polarization. Because of the dislocation, the electronic and magnetic inversion centers do not coincide, which turns out to be a sufficient condition for multiferroic coupling. The novel mechanism explains the formation of multiferroic phases at the magnetic commensurability transitions, such as the ones observed in ${\mathrm{YMn}}_2{\mathrm{O}}_5$ and related compounds. We predict that in these multiferroics an oscillating electrical polarization is concomitant with the uniform polarization. On the basis of our theory, we put forward new types of magnetic materials that are potentially ferroelectric.

We demonstrate experimentally a procedure to obtain the maximum efficiency for the storage and retrieval of light pulses in atomic media. The procedure uses time-reversal to obtain optimal input signal pulse shapes. Experimental results in warm Rb vapor are in good agreement with theoretical predictions and demonstrate a substantial improvement of efficiency. This optimization procedure is applicable to a wide range of systems.

The breakout reaction ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$, which regulates the flow between the hot CNO cycle and the $rp$ process, is critical for the explanation of the burst amplitude and periodicity of x-ray bursters. We report on the first successful measurement of the critical $\alpha$-decay branching ratios of relevant states in ${}^{19}\mathrm{Ne}$ populated via ${}^{19}\mathrm{F}({}^3\mathrm{He},t){}^{19}\mathrm{Ne}$. Based on the experimental results and our previous lifetime measurements of these states, we derive the first experimental rate of ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$. The impact of our experimental results on the burst pattern and periodicity for a range of accretion rates is analyzed.

The static dielectric properties of liquid and solid water are investigated within linear response theory in the context of ab initio molecular dynamics. Using maximally localized Wannier functions to treat the macroscopic polarization we formulate a first-principles, parameter-free, generalization of Kirkwood’s phenomenological theory. Our calculated static permittivity is in good agreement with experiment. Two effects of the hydrogen bonds, i.e., a significant increase of the average local moment and a local alignment of the molecular dipoles, contribute in almost equal measure to the unusually large dielectric constant of water.

The MiniBooNE Collaboration reports first results of a search for ${\nu }_e$ appearance in a ${\nu }_{\mu }$ beam. With two largely independent analyses, we observe no significant excess of events above the background for reconstructed neutrino energies above 475 MeV. The data are consistent with no oscillations within a two-neutrino appearance-only oscillation model.

We study the structure of numerically simulated hard sphere packings at different densities by investigating local tetrahedral configurations of the spheres. Clusters of tetrahedra adjacent by faces present relatively dense aggregates of spheres atypical for crystals. The number of spheres participating in such polytetrahedral configurations increases with densification of the packing, and at the Bernal’s limiting density (the packing fraction around 0.64) all spheres of the packing become involved in such tetrahedra. Thus the polytetrahedral packing cannot provide further increase in the density, and alternative structural change (formation of crystalline nuclei) begins henceforth.

Recent calculations of the recoil velocity in binary black-hole mergers have found the kick velocity to be of the order of a few hundred $\mathrm{km}/\mathrm{s}$ in the case of nonspinning binaries and about $500\mathrm{km}/\mathrm{s}$ in the case of spinning configurations, and have lead to predictions of a maximum kick of up to $1300\mathrm{km}/\mathrm{s}$. We test these predictions and demonstrate that kick velocities of at least $2500\mathrm{km}/\mathrm{s}$ are possible for equal-mass binaries with antialigned spins in the orbital plane. Kicks of that magnitude are likely to have significant repercussions for models of black-hole formation, the population of intergalactic black holes, and the structure of host galaxies.

Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of $\sim 4000\mathrm{km}{\mathrm{s}}^{-1}$ for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger.

We attribute a strong forward directed THz emission from femtosecond laser filaments in air to a transition-Cherenkov emission from the plasma space charge moving behind the ionization front at light velocity. Distant targets can be easily irradiated by this new source of THz radiation.

We report, for the first time, laser spectroscopy of the clock transition in . A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminum’s electronic state to the beryllium’s hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency . They are also used to measure the lifetime of the metastable clock state , the ground state factor , and the excited state factor , in units of the Bohr magneton.

I discuss some simple aspects of the low-energy physics of a nontrivial scale invariant sector of an effective field theory—physics that cannot be described in terms of particles. I argue that it is important to take seriously the possibility that the unparticle stuff described by such a theory might actually exist in our world. I suggest a scenario in which some details of the production of unparticle stuff can be calculated. I find that in the appropriate low-energy limit, unparticle stuff with scale dimension $d_{\mathcal{U}}$ looks like a nonintegral number $d_{\mathcal{U}}$ of invisible particles. Thus dramatic evidence for a nontrivial scale invariant sector could show up experimentally in missing energy distributions.