Strong infrared fields can be used for controlled spinning of molecules to very high angular momentum states. The angular momentum acquired can be sufficient to break molecular bonds. The approach is suitable for all anisotropic molecules, and we illustrate it by dissociating a homonuclear diatomic ${\mathrm{Cl}}_2$, with optical centrifuge efficiently separating ${\mathrm{Cl}}^{35}$ and ${\mathrm{Cl}}^{37}$ isotopes and thus demonstrating high sensitivity to the moment of inertia.

The analysis of small- and ultra-small-angle neutron scattering data for sedimentary rocks shows that the pore-rock fabric interface is a surface fractal $(D_s=2.82\mathrm{})$ over 3 orders of magnitude of the length scale and 10 orders of magnitude in intensity. The fractal dimension and scatterer size obtained from scanning electron microscopy image processing are consistent with neutron scattering data.

A fourth-order Young interference experiment was done to demonstrate a practical way to measure the de Broglie wavelength of a two-photon wave packet. A two-photon collinear beam is generated by type-II spontaneous parametric down-conversion. By modifying the transverse field profile of the pump laser beam that generates the two-photon beam we demonstrate that it is possible to measure the de Broglie wavelength of the single-photon constituents of the two-photon wave packet, the de Broglie wavelength of the two-photon wave packet as a whole and an ill defined intermediate de Broglie wavelength between the two cases.

The dynamics of atomic steps and the interactions between them were observed by in situ scanning electron microscopy for the sublimation of a Si(111) surface which was atomically flat on a large $(\sim 100\mu \mathrm{m}\times 50\mu \mathrm{m})$ scale. Newly nucleated widely spaced steps moved at a constant velocity. For more narrowly spaced steps, diffusion mediated step-step interactions reduced the step velocity. To further probe these interactions, steps were made to collide. In destructive collisions, steps decelerated and flattened. In constructive collisions double atomic steps were produced.

The effect of impurities on the surface and interfacial melting of ice is investigated in the context of the Derjaguin-Landau-Verwey-Overbeek theory by calculating van der Waals and Coulombic interactions within interfacial solution films. At high temperatures, the classical solute effect dominates the melting behavior. However, depending on the amount of impurity, as temperature decreases the slope of the film-thickness versus temperature curve changes in a manner that depends on the relative strengths of van der Waals and Coulombic interactions. The results explain the wide range of experimental discrepancies and hence impact a host of environmental phenomena.

Recently, Arkani-Hamed, Dimopoulos, and Dvali have proposed that there are extra compact dimensions of space, accessible to gravity but not to ordinary matter, which could be macroscopically large. In this Letter, we argue that high-energy collider processes in which gravitons are radiated into these new dimensions place significant, model-independent constraints on this picture. We present the constraints from anomalous single photon production at $e^{+}{e}^{-}$ colliders and from monojet production at hadron colliders.

We report the direct observation of internal layering in thin ( $\sim 45–90Å$) liquid films of nearly spherical, nonpolar molecules, tetrakis(2-ethylhexoxy)silane, using synchrotron x-ray reflectivity. The Patterson functions have secondary maxima indicating layer formation, and model-independent fitting to the reflectivity data shows that there are three electron density oscillations near the solid-liquid interface, with a period of $\sim 10Å$ (consistent with the molecular dimensions). The oscillation amplitude has a strong inverse dependence on the substrate surface roughness.

The combination of semiconductor quantum well structures and strongly piezoelectric crystals leads to a system in which surface acoustic waves with very large amplitudes can interact with charge carriers in the well. The surface acoustic wave induces a dynamic lateral superlattice potential in the plane of the quantum well which is strong enough to spatially break up a two-dimensional electron system into moving wires of trapped charge. This transition is manifested in an increase of the electron transport velocity with sound amplitude, eventually reaching the sound velocity. The sound absorption by the electron system then becomes governed by nonlinearities and is strongly reduced. We study the transition from the linear towards the strongly nonlinear regime of interaction and present a theoretical description of such phenomena in a 2D system.

Experimental observations of pulsed ultrasonic transmission through granular glass beads under oedometric loading are presented. We observe in the transmitted signals the coexistence of a coherent ballistic pulse traveling through an “effective contact medium” and a specklelike multiply scattered signal. The relative amplitudes of these signals strongly depend on the ratios of the bead size to the wavelength and to the detector size. Experimental data support recent descriptions of the inhomogeneous stress field within granular media.

We report measurements of mm-wavelength radiation from two-dimensional arrays of underdamped Josephson junctions. All of our samples emit coherently in a novel synchronized state, which is triggered by a resonance in the array structure. Measurements of the detected power as a function of the number $N$ of active junctions show a threshold, suggesting population inversion. Above threshold, the power scales with $N^2$ up to an array size bigger than the free-space radiation wavelength. The highest measured conversion efficiency from dc to ac power is about 17%. Our data are consistent with stimulated emission causing coherence and cannot be explained by existing classical coupling mechanisms.

A new laser-accelerator injector based on the high-energy electrons ejected from a laser focus following the ionization of high-charge states of gases has been investigated. This method can generate electron pulses with MeV energies and pulse widths substantially less than the laser pulse width using terawatt lasers. Experiments at intensities of $3\times {10}^{18}\mathrm{W}/\mathrm{cm}{}^2$ show that two highly directional electron beams with energies up to 340 keV are produced in the laser polarization direction. These highly directional beams are inconsistent with simulation results using Ammosov-Delone-Krainov (ADK) tunneling theory to model the ionization process. It is shown that this is likely due to the release of electrons with larger canonical momentum than predicted by ADK theory.

The breakup of ${}^{12}\mathrm{Be}$ into ${}^6\mathrm{He}{+}^6\mathrm{He}$ and ${}^4\mathrm{He}{+}^8\mathrm{He}$ has been studied using a 378 MeV ${}^{12}\mathrm{Be}$ beam inelastically excited by ${}^{12}\mathrm{C}$ and $({\mathrm{CH}}_2{)}_n$ targets. The measurements indicate that breakup occurs from rotational states in the 10 to 25 MeV excitation energy interval, with spins in the range of $4ħ$ to $8ħ$. The inferred moment of inertia is consistent with the cluster decay of an exotic molecular structure in ${}^{12}\mathrm{Be}$, which may be associated with an $\alpha -4n-\alpha$ cluster configuration.

Recent molecular level studies of energy dissipation in sliding friction have suggested a contribution from adhesive forces. In order to observe this directly, we have constructed a scanning force microscope with decoupled lateral and normal force sensors to simultaneously observe the onset of both friction and attractive forces. Measurements made on self-assembling alkanethiol films with chemically different tail groups show that friction can increase with stronger adhesive intermolecular forces and from the associated tensile deformation and collective motion of the thiol chains.

We show the design and preparation of a novel type of magnet exhibiting two compensation temperatures; i.e., the spontaneous magnetization changes its sign twice with changing temperature. The key to obtaining this unusual behavior is the simultaneous incorporation of one antiferromagnetic and two different ferromagnetic interactions through the use of four different spin sources, as predicted by a calculation based on molecular field theory. As a prototype exemplifying this idea, we have prepared a Prussian blue analog, $\left({\mathrm{Ni}}_{0.22}^{\mathrm{II}}{\mathrm{Mn}}_{0.60}^{\mathrm{II}}{\mathrm{Fe}}_{0.18}^{\mathrm{II}}{)}_{1.5}\right[{\mathrm{Cr}}^{\mathrm{III}}\left(\mathrm{CN}{)}_6\right]̇7.6{\mathrm{H}}_2\mathrm{O}$, which exhibits magnetization reversals at 35 and 53 K.

We propose a new system for implementing quantum logic gates: neutral atoms trapped in a very far-off-resonance optical lattice. Pairs of atoms are made to occupy the same well by varying the polarization of the trapping lasers, and then a near-resonant electric dipole is induced by an auxiliary laser. A controlled-NOT can be implemented by conditioning the target atomic resonance on a resolvable level shift induced by the control atom. Atoms interact only during logical operations, thereby suppressing decoherence.

Fluids adsorbed in microporous materials can exhibit quantum sieving, where heavy isotopes are preferentially adsorbed over light isotopes. We present the first detailed predictions of quantum sieving based on realistic models of microporous materials. Carbon nanotubes, and the interstices of nanotube bundles, can act as highly effective quantum sieves for hydrogen isotopes. Quantum sieving of He and Ne in the zeolite ${\mathrm{AlPO}}_4-22$ is also discussed.

We study the propagation of an elastic excitation through a magnetorheological slurry made of hydrogen-reduced iron particles suspended in glycerine. Two different low-frequency longitudinal modes are observed, the second of them appearing as soon as a magnetic field is applied to the fluid. The first mode travels through glycerine channels within the suspension, whereas the second one propagates through the fibrillated structure formed by the iron particles. This second mode is very strong in amplitude and travels at lower speeds, depending on the magnetic field intensity.

The ground-state band of the $Z=102\mathrm{}$ isotope ${}^{254}\mathrm{No}$ has been identified up to spin 14, indicating that the nucleus is deformed. The deduced quadrupole deformation, $\beta =0.27\mathrm{}$, is in agreement with theoretical predictions. These observations confirm that the shell-correction energy responsible for the stability of transfermium nuclei is partly derived from deformation. The survival of ${}^{254}\mathrm{No}$ up to spin 14 means that its fission barrier persists at least up to that spin.

Scanning tunneling microscopy studies of etching of $\mathrm{Si}\left(100\right)-(2\times 1)$ show that the rate of terrace pit formation goes through a maximum for surface coverages of $\theta \left(\mathrm{Cl}\right)=0.77\mathrm{}\pm 0.05\mathrm{monolayer}$, in contrast to predictions of conventional models. Using recently calculated energies for different possible surface configurations, we show that a key component in desorption is the formation of a single-atom vacancy adjacent to a volatile ${\mathrm{SiCl}}_2$ unit. The demonstration of vacancy-assisted reaction establishes a self-limited reaction and the sequence of events leading to desorption.