103 research outputs found
Guiding slow polar molecules with a charged wire
We demonstrate experimentally the guiding of cold and slow ND3 molecules
along a thin charged wire over a distance of ~0.34 m through an entire
molecular beam apparatus. Trajectory simulations confirm that both linear and
quadratic high-field-seeking Stark states can be efficiently guided from the
beam source up to the detector. A density enhancement up to a factor 7 is
reached for decelerated beams with velocities ranging down to ~50 m/s generated
by the rotating nozzle technique
Coherent cooperative fluorescence resonance energy transfer
Cooperative fluorescence resonance energy transfer effect is experimentally demonstrated for a few crystals doped with rare-earth ions. We show that, at the liquid helium temperatures in similar crystals, coherent cooperative fluorescence resonance energy transfer, as well as an inverse coherent up-conversion process, could be observed, and briefly discuss possible applications of these effects
Application of the Mathieu’s equation for a design of a photonic crystal supporting surface electromagnetic waves
Nowadays, unique characteristics of surface electromagnetic waves, particularly, surface plasmons supported by a specially designed photonic crystal find numerous applications. We propose to exploit an evident analogy between such a photonic crystal and a structure with a sine-modulated refractive index. The light propagation inside the latter is described by the famous Mathieu’s differential equation. This application of the Mathieu’s equation can be useful for a design of multilayer structures, and also for fundamental understanding of electromagnetic phenomena in inhomogeneous media
Near-field scanning optical microscopy using polymethylmethacrylate optical fiber probes
We report the first use of polymethylmethacrylate (PMMA) optical fiber-made probes for scanning near-field optical microscopy (SNOM). The sharp tips were prepared by chemical etching of the fibers in ethyl acetate, and the probes were prepared by proper gluing of sharpened fibers onto the tuning fork in the conditions of the double resonance (working frequency of a tuning fork coincides with the resonance frequency of dithering of the free-standing part of the fiber) reported earlier for the case of glass fibers. Quality factors of the probes in the range 2000–6000 were obtained, which enables the realization of an excellent topographical resolution including state-of-art imaging of single DNA molecules. Near-field optical performance of the microscope is illustrated by the Photon Scanning Tunneling Microscope images of fluorescent beads with a diameter of 100 nm. The preparation of these plastic fiber probes proved to be easy, needs no hazardous material and/or procedures, and typical lifetime of a probe essentially exceeds that characteristic for the glass fiber probe
Force spectroscopy of barnase-barstar single molecule interaction
Results of the single molecule force spectroscopy study of specific interactions between ribonuclease barnase and its inhibitor barstar are presented. Experimental data obtained for the force loading rate ranging 2-70 nN/s are well approximated by a single straight line, from which the dissociation barrier of the width of 0.12 nm and height of 0.75-0.85X10(-19) J can be inferred. The measured value of specific interaction does not depend on the NaCl concentration. This apparently contradicts the well-known dependence of the binding energy of this pair on the salt concentration, but such a "contradiction" is explained by the insensitivity of the force spectroscopy data to the relatively long-range electrostatic interaction. The latter essentially contributes to the value of barnase-barstar binding energy revealed by biochemical measurements, and it is exactly this electrostatic interaction which is influenced by the salt concentration. Copyright (C) 2010 John Wiley & Sons, Ltd
Slowing and cooling molecules and neutral atoms by time-varying electric field gradients
A method of slowing, accelerating, cooling, and bunching molecules and
neutral atoms using time-varying electric field gradients is demonstrated with
cesium atoms in a fountain. The effects are measured and found to be in
agreement with calculation. Time-varying electric field gradient slowing and
cooling is applicable to atoms that have large dipole polarizabilities,
including atoms that are not amenable to laser slowing and cooling, to Rydberg
atoms, and to molecules, especially polar molecules with large electric dipole
moments. The possible applications of this method include slowing and cooling
thermal beams of atoms and molecules, launching cold atoms from a trap into a
fountain, and measuring atomic dipole polarizabilities.Comment: 13 pages, 10 figures. Scheduled for publication in Nov. 1 Phys. Rev.
Discrete structure of ultrathin dielectric films and their surface optical properties
The boundary problem of linear classical optics about the interaction of
electromagnetic radiation with a thin dielectric film has been solved under
explicit consideration of its discrete structure. The main attention has been
paid to the investigation of the near-zone optical response of dielectrics. The
laws of reflection and refraction for discrete structures in the case of a
regular atomic distribution are studied and the structure of evanescent
harmonics induced by an external plane wave near the surface is investigated in
details. It is shown by means of analytical and numerical calculations that due
to the existence of the evanescent harmonics the laws of reflection and
refraction at the distances from the surface less than two interatomic
distances are principally different from the Fresnel laws. From the practical
point of view the results of this work might be useful for the near-field
optical microscopy of ultrahigh resolution.Comment: 25 pages, 16 figures, LaTeX2.09, to be published in Phys.Rev.
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