Experimental observations of time-delay-induced amplitude death in two coupled nonlinear electronic circuits that are individually capable of exhibiting limit-cycle oscillations are described. The existence of multiply connected death islands in the parameter space of coupling strength and time delay for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds [Phys. Rev. Lett. 80, 5109 (1998); Physica (Amsterdam) 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay, and the onset of both in-phase and antiphase collective oscillations.

A quantitative study of the long-range interaction between single copper adatoms on Cu(111) mediated by the electrons in the two-dimensional surface-state band is presented. The interaction potential was determined by evaluating the distance distribution of two adatoms from a series of scanning tunneling microscopy images taken at temperatures of 9–21 K. The long-range interaction is oscillatory with a period of half the Fermi wavelength and decays for larger distances $d$ as $1/d^2$. Five potential minima were identified for separations of up to 70 Å. The interaction significantly changes the growth of Cu/Cu(111) at low temperatures.

We have demonstrated experimentally that polar molecules revolve around the inner electrode of a charged cylindrical capacitor in helical trajectories that result from a superposition of a translational motion along and an orbital motion around the cylinder axis. In this way molecular beams can be guided over any given distance. The results have been obtained for nozzle beams of NaCl, NaBr, and NaI seeded in Kr. The capacitor bent into a toroid may be used as a storage ring for polar molecules in high field seeking rotational states.

Scanning probe microscopy (SPM) can be expanded to volume imaging. As an example, the core of a dislocation within the three-dimensional (3D) spatial microdomain structure of poly(styrene-block-butadiene-block-styrene) was imaged with $\approx 10\mathrm{nm}$ resolution. The specimen was eroded step by step and its chemical composition in layers beneath the original surface was imaged with SPM. Similar to computed tomography, the 3D distribution of polystyrene and polybutadiene was reconstructed from a series of images. This approach might provide a simple means for real-space volume imaging with nanometer and even atomic resolution of various materials and physical properties.

The fact that the melting points of nanoparticles are always lower than those of the corresponding bulk material is a paradigm supported by extensive experimental data for a large number of systems and by numerous calculations. Here we demonstrate that tin cluster ions with 10–30 atoms remain solid at $\sim 50$ K above the melting point of bulk tin. This behavior is possibly related to the fact that the structure of the clusters is completely different from that of the bulk element.

A molecular beam consisting of small helium clusters is diffracted from a 100 nm period transmission grating. The relative dimer intensities have been measured out to the 7th order and are used to determine the reduction of the effective slit width resulting from the finite size of the dimer. From a theoretical analysis of the data which also takes into account the van der Waals interaction with the grating bars, the bond length (mean internuclear distance) and the binding energy are found to be $〈r〉=52\mathrm{}\pm 4Å$ and $|E_b|=1.1+0.3\mathrm{}/-0.2\mathrm{}$ mK.

Matter between contiguous crystallites is assimilated to a thin elastic plate immersed in a different elastic medium. It is shown that a shear stress exceeding a critical value should corrugate the boundary and induce periodic normal stress fields in the two adjacent crystal surfaces, which cause motion of vacancies in closed loops between the two crystals. The consequent cyclic transport of atoms in the opposite sense determines crystal sliding at a temperature dependent relative speed. Most of the phenomenology of superplastic allows follows in a quantitative manner.

We have succeeded in observing nuclear excitation by electron transition (NEET) in ${}^{197}\mathrm{Au}$ by a new method. Monochromatic x-rays of synchrotron radiation were used to ionize the $K$ shell of gold atoms in a target foil. The internal-conversion electrons emitted from excited nuclei were detected with a silicon avalanche photodiode. At a photon energy of 80.989 keV, the NEET probability in ${}^{197}\mathrm{Au}$ was determined to be $(5.0\pm 0.6)\times {10}^{-8\mathrm{}}$ from a comparison of the event number per photon between NEET and the nuclear resonance at 77.351 keV.

Resonant formation of $d\mu t$ molecules in collisions of muonic tritium ( $\mu t$) on ${\mathrm{D}}_2$ was investigated using a beam of $\mu t$ atoms, demonstrating a new direct approach in muon catalyzed fusion studies. Strong epithermal resonances in $d\mu t$ formation were directly revealed for the first time. From the time-of-flight analysis of $2036\pm 116$ $\mathrm{dt}$ fusion events, a formation rate consistent with $0.73\pm (0.16{)}_{\mathrm{meas}}\pm (0.09{)}_{\mathrm{model}}$ times the theoretical prediction was obtained. For the largest peak at a resonance energy of $0.423\pm 0.037\mathrm{eV}$, this corresponds to a rate of $(7.1\pm 1.8)\times {10}^9{\mathrm{s}}^{-1\mathrm{}}$, more than an order of magnitude larger than those at low energies.

In situ high-temperature, high resolution transmission electron microscopy (HRTEM) was performed on an Al-Cu-Co decagonal quasicrystal, to investigate thermal fluctuation of phasons. A tiling pattern constructed from the HRTEM image was analyzed in the framework of the strip-projection method. Transitions between two local tile arrangements were observed at high temperature for the first time, and were shown to correspond to a thermal phason fluctuation.

Cold dark matter (CDM) models predict small-scale structure in excess of observations of the cores and abundance of dwarf galaxies. These problems might be solved, and the virtues of CDM models retained, even without postulating ad hoc dark matter particle or field interactions, if the dark matter is composed of ultralight scalar particles $\left(m\sim {10}^{-22\mathrm{}}\mathrm{eV}\right)$, initially in a (cold) Bose-Einstein condensate, similar to axion dark matter models. The wave properties of the dark matter stabilize gravitational collapse, providing halo cores and sharply suppressing small-scale linear power.

We point out that for solar neutrino oscillations with the mass-squared difference of $\Delta m^2\sim {10}^{-10\mathrm{}}–{10}^{-9\mathrm{}}{\mathrm{eV}}^2$, i.e., in the so-called vacuum oscillation range, the solar matter effects are non-negligible, particularly for the low energy $\mathrm{pp}$ neutrinos. One consequence of this is that the values of the mixing angle $\theta$ and $\pi /2-\theta$ are not equivalent, making it necessary to consider the entire physical range of the mixing angle $0\le \theta \le \pi /2$ when determining the allowed values of the neutrino oscillation parameters.

A new mechanism for electron emission from planar cathodes is described. The theoretical analysis shows that, with an ultrathin wide band-gap semiconductor layer (UTSC) on a metal, the surface barrier is lowered to $\sim 0.1\mathrm{eV}$ due to the creation of a space charge induced by the electrons injected from the metal. The barrier height depends mostly on the UTSC thickness and not on the state of the surface, as in thermionic and field emissions. This mechanism explains the measured stable emission at 300 K and ${10}^{-7\mathrm{}}\mathrm{Torr}$, with a threshold field of only $\sim 50\mathrm{V}/\mu \mathrm{m}$, from these solid-state field-controlled emitters.

The wavelength of the ${}^{57}\mathrm{Fe}$ Mössbauer radiation is measured with a relative uncertainty of 0.19 ppm by using almost exact Bragg backscattering from a reference silicon crystal. Its value is determined as ${\lambda }_{\mathrm{M}}=0.860\mathrm{}25474\left(16\right)\times {10}^{-10\mathrm{}}$ m. The corresponding Mössbauer photon energy is $E_{\mathrm{M}}=14\mathrm{}412.497\left(3\right)$ eV. The wavelength of the ${}^{57}\mathrm{Fe}$ Mössbauer radiation is easily reproducible with an accuracy of at least ${10}^{-11\mathrm{}}{\lambda }_{\mathrm{M}}$ and could be used as a length standard of atomic dimensions.

The phase evolution of light in an optical waveguide structure has for the first time been visualized with subwavelength resolution using a novel heterodyne interferometric photon scanning tunneling microscope. Phase singularities in the optical field of the waveguide have been observed. The phase singularities of charge one appear at locations where the modal field amplitude vanishes, due to the interference of various modes in the waveguide. Excellent agreement of the data with calculations has been obtained.

We report observations of electromagnetic wave-induced 557.7-nm emission in correspondence with a sporadic low-altitude plasma layer (the sporadic- $E$ layer, $E_s$). We show that the structure of 557.7-nm emission seen for some events results from a transformation of transmitted energy by ionization clouds, compiling the patchy type $E_s$, and presents a projection of the sporadic- $E$ layer structure on the emission altitude. This allows us to propose the first method for visualizing a horizontal structure of sporadic- $E$ layers.

Photoelectric charging measurements are presented of dust grains in vacuum for isolated grains and for grains near a photoemissive surface. Isolated grains reach a positive-equilibrium floating potential, dependent upon the work function of the particle, which causes the emitted electrons to be returned. Grains dropped past a photoemitting surface reach a negative floating potential for which the sum of the emitted and collected currents is zero. The particles tested are $90–106\mu \mathrm{m}$ in diameter and are composed of Zn, Cu, graphite, and glass.

The Cryogenic Dark Matter Search (CDMS) employs Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. CDMS data, accounting for the neutron background, give limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude unexplored parameter space above $10\mathrm{GeV}/c^2$ WIMP mass and, at $>75\mathrm{}\%$ C.L., the entire $3\sigma$ allowed region for the WIMP signal reported by the DAMA experiment.

Phase-matched relativistic harmonic generation in plasmas is observed for the first time. Third-harmonic light is detected and discriminated spectrally and angularly from the harmonics generated from competing processes. Its angular pattern is a narrow forward-directed cone, which is consistent with phase matching of a high-order transverse mode in a plasma. The signal level is found to be on the same order of magnitude for a circularly polarized pump pulse as for a linearly polarized pump pulse.

The mechanical response of 15 single wall carbon nanotube (SWCNT) ropes under tensile load was measured. For 8 of these ropes strain data were obtained and they broke at strain values of $5.3\%$ or lower. The force-strain data are well fit by a model that assumes the load is carried by the SWCNTs on the perimeter of each rope. This model provides an average breaking strength of SWCNTs on the perimeter of each rope; the 15 values range from 13 to 52 GPa (mean 30 GPa). Based on the same model the 8 average Young's modulus values determined range from 320 to 1470 GPa (mean 1002 GPa).