We demonstrate a great simplification in the long-standing problem of measuring optical frequencies in terms of the cesium primary standard. An air-silica microstructure optical fiber broadens the frequency comb of a femtosecond laser to span the optical octave from 1064 to 532 nm, enabling us to measure the 282 THz frequency of an iodine-stabilized Nd:YAG laser directly in terms of the microwave frequency that controls the comb spacing. Additional measurements of established optical frequencies at 633 and 778 nm using the same femtosecond comb confirm the accepted uncertainties for these standards.

The possibility of observing superluminal behavior in the propagation of localized microwaves over distances of tens of wavelengths is experimentally demonstrated. These types of waves, better than the evanescent modes of tunneling, can contribute to answering the question on the luminal limit of the signal velocity.

The variation of a magnetic field as a function of depth beneath the surface of an ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ thin film in the Meissner state has been measured using low energy muons. The depth of implantation was varied from 20–150 nm by tuning the energy of the implanted muons from 3–30 keV. These are direct measurements of the penetration of a magnetic field beneath a superconducting surface which illustrate the power of low energy muons for near surface studies in superconductivity and magnetism.

In a closed volume of molten sodium an intense single-vortex-like helical flow has been produced by an outside powered propeller. At a flow rate of $0.67{\mathrm{m}}^3/\mathrm{s}$ a slowly growing magnetic field eigenmode was detected. For a slightly lower flow, additional measurements showed a slow decay of this mode. The measured results correspond satisfactorily with numerical predictions for the growth rates and frequencies.

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system $\left[\mathrm{Pt}\right(\mathrm{en}{)}_2\left]\right[\mathrm{Pt}\left(\mathrm{en}{)}_2{\mathrm{Br}}_2\right]̇({\mathrm{PF}}_6{)}_4$ ( $\mathrm{en}=\mathrm{ethylene}-\mathrm{diamine}$, ${\mathrm{C}}_2{\mathrm{H}}_8{\mathrm{N}}_2$), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at $\sim 110{\mathrm{cm}}^{-1\mathrm{}}$ accompanies the formation of the self-trapped exciton on a $\sim 200\mathrm{fs}$ time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.

We present an experimental study of the thermal response to a positive temperature quench in two-phase fluid ${\mathrm{SF}}_6$ in low gravity for temperature ranging from $10.1$ to $0.1$ K from the critical temperature. The temperature was measured simultaneously in the gas, the liquid, and the cell wall by thermistors and the density distribution was observed by interferometry. During the quench the gas temperature considerably exceeded the temperature of the heating walls (overheating up to $23\%$). This striking observation is discussed in the light of the adiabatic heat transfer in this highly compressible fluid while the key role of the localization in low gravity of the gas and liquid phases is revealed.

We describe a general technique that allows for an ideal transfer of quantum correlations between light fields and metastable states of matter. The technique is based on trapping quantum states of photons in coherently driven atomic media, in which the group velocity is adiabatically reduced to zero. We discuss possible applications such as quantum state memories, generation of squeezed atomic states, preparation of entangled atomic ensembles, quantum information processing, and quantum networking.

We present a novel approach to the preparation of neutral (anti-)matter. The scheme is based on recombination of a free electron and an ion, and can be considered as the inverse of pulsed field ionization. We have obtained promising results on rubidium: at low densities already efficiencies of $0.3\%$ were obtained. This is orders of magnitude more than has been achieved in previous recombination studies.

The apparent lack of suitable astrophysical sources for the observed highest energy cosmic rays within $\approx 20\mathrm{Mpc}$ is the “Greisen-Zatsepin-Kuzmin (GZK) paradox.” We constrain representative models of the extragalactic magnetic field structure by Faraday rotation measurements; limits are at the $\mu \mathrm{G}$ level rather than the nG level usually assumed. In such fields, even the highest energy cosmic rays experience large deflections. This allows nearby active galactic nuclei (possibly quiet today) or gamma ray bursts to be the source of ultrahigh energy cosmic rays without contradicting the GZK distance limit.

We propose a mechanism for experimental investigation of relativistic effects in the laser-atom interaction with moderate (nonrelativistic) laser intensities that involves placing the system in a static magnetic field parallel to the laser's magnetic-field component. The resonantly induced relativistic motion of the atomic electron leads to a variety of novel phenomena: a relativistic dephasing leading to a ringlike spatial probability density, a counterintuitive window of relativistically enhanced motion, and a sequence of sawtooth-shaped resonances that may increase the harmonic generation.

A steady-state, fully noninductive plasma current has been sustained for the first time in a tokamak using electron cyclotron current drive only. In this discharge, 123 kA of current have been sustained for the entire gyrotron pulse duration of 2 s. Careful distribution across the plasma minor radius of the power deposited from three 0.5-MW gyrotrons was essential for reaching steady-state conditions. With central current drive, up to 153 kA of current have been fully replaced transiently for 100 ms. The noninductive scenario is confirmed by the ability to recharge the Ohmic transformer. The dependence of the current drive efficiency on the minor radius is also demonstrated.

Novel implementation of the Fourier imaging technique on conduction electron spins in the one-dimensional organic conductors $(\mathrm{FA}{)}_2{\mathrm{PF}}_6$ (FA: fluoranthene) is reported. Two-dimensional spatial imaging of resolution $30\mu {\mathrm{m}}^2$ is combined with the pulsed-gradient spin-echo technique, to derive maps revealing the local properties of the electron spin density and mobility. The maps generally show pronounced inhomogeneity of both density and mobility on the scale of $\sim 30–300\mu \mathrm{m}$. Highly mobile regions were identified to exist, and the mobility in these was quantitatively evaluated by a basic theoretical model of restricted diffusion.

A low temperature scanning force microscope (SFM) operating in a dynamic mode in ultrahigh vacuum was used to study the Si(111)- $(7\times 7)$ surface at 7.2 K. Not only the twelve adatoms but also the six rest atoms of the unit cell are clearly resolved for the first time with SFM. In addition, the first measurements of the short range chemical bonding forces above specific atomic sites are presented. The data are in good agreement with first principles computations and indicate that the nearest atoms in the tip and sample relax significantly when the tip is within a few Å of the surface.

Scanning tunneling microscopy was used to study molecular order in monolayer organic films formed by solution-phase growth from thermotropic liquid crystal solvents. The films develop macroscopically uniaxial alignment, with adlayer orientation controlled by an external magnetic field through interactions mediated by the liquid crystal. Results are presented for two films deposited from nematic and smectic- $A$ solvents, along with a discussion of the alignment mechanism.

The faceting of monocrystals of the lyotropic cubic liquid crystals in equilibrium with a humid atmosphere is observed. Experiments reveal the presence of more than 60 different types of facets on the surface of a spherical crystal of radius $R=1\mathrm{}\mathrm{mm}$. The devil's staircase type of faceting has been predicted theoretically when the interaction between steps on the crystal surface is repulsive.

Modern data are showing increasing evidence that the Universe is accelerating. So far, all attempts to account for the acceleration have required some fundamental dimensionless quantities to be extremely small. We show how a class of scalar field models (which may emerge naturally from superstring theory) can account for acceleration which starts in the present epoch with all the potential parameters $O\left(1\right)$ in Planck units.

Making use of self-assembly techniques, we realize nanoscopic semiconductor quantum rings in which the electronic states are in the true quantum limit. We employ two complementary spectroscopic techniques to investigate both the ground states and the excitations of these rings. Applying a magnetic field perpendicular to the plane of the rings, we find that, when approximately one flux quantum threads the interior of each ring, a change in the ground state from angular momentum $\ell =0\mathrm{}$ to $\ell =-1\mathrm{}$ takes place. This ground state transition is revealed both by a drastic modification of the excitation spectrum and by a change in the magnetic-field dispersion of the single-electron charging energy.

Reversible conductance transitions are demonstrated on the molecular scale in a complex of 3-nitrobenzal malononitrile and 1,4-phenylenediamine, by application of local electric field pulses. Both macroscopic and local current-voltage (I/V) measurements show similar electrical bistability behavior. The mechanism of the electrical bistability is discussed.

We experimentally demonstrate resonant coupling between photons and excitons in microcavities which can efficiently generate enormous single-pass optical gains approaching 100. This new parametric phenomenon appears as a sharp angular resonance of the incoming pump beam, at which the moving excitonic polaritons undergo very large changes in momentum. Ultrafast stimulated scattering is clearly identified from the exponential dependence on pump intensity. This device utilizes boson amplification induced by stimulated energy relaxation.

A streak camera with high spatial and temporal resolution was used for imaging the dynamics of the violent collapse in single-bubble sonoluminescence. The high pressure in the last phase of the bubble collapse leads to the emission of a shock wave, which is launched with a shock velocity of almost 4000 m/s. The shock amplitude decays much faster than $\sim 1/r$. From the strongly nonlinear propagation the pressure in the vicinity of the bubble can be calculated to be in the range of 40–60 kbar.