Precision absolute frequency laser spectroscopy of argon II in parallel and antiparallel geometry using a frequency comb for calibration

A collinear fast ion beam laser apparatus was constructed and tested. It will be used on-line to the SLOW RI radioactive beam facility in RIKEN (Japan) and as in the present experiment for precision absolute frequency measurements of astrophysically important reference lines. In the current work we conducted absolute measurements of spectral lines of Ar ions using parallel and antiparallel geometries. To provide a reference for the laser wavelength iodine saturation spectroscopy was used. The precision of this reference was enhanced by simultaneously observing the beat node between the spectroscopy laser and the corresponding mode of a femtosecond laser frequency comb. When performing collinear and anticollinear measurements simultaneously for the laser induced fluorescence, the exact relativistic formula for the transition frequency v0 = pvcoll � vanticoll can be applied. In this geometry ion source instabilities due to pressure and anode voltage fluctuation are minimized. The procedure of fluorescence lineshapes fitting is discussed and the errors in the measurements are estimated. The result is v0 = 485, 573, 619.7 � 0.3MHz corresponding to (delta v)/v = 6 � 10?10 and is an improvement of two orders of magnitude over the NIST published value

Sensitive detection of voltage transients using differential intensity surface plasmon resonance system

This paper describes theoretical and experimental study of the fundamentals of using surface plasmon resonance (SPR) for label-free detection of voltage. Plasmonic voltage sensing relies on the capacitive properties of metal-electrolyte interface that are governed by electrostatic interactions between charge carriers in both phases. Externally-applied voltage leads to changes in the free electron density in the surface of the metal, shifting the SPR position. The study shows the effects of the applied voltage on the shape of the SPR curve. It also provides a comparison between the theoretical and experimental response to the applied voltage. The response is presented in a universal term that can be used to assess the voltage sensitivity of different SPR instruments. Finally, it demonstrates the capacity of the SPR system in resolving dynamic voltage signals; a detection limit of 10mV with a temporal resolution of 5ms is achievable. These findings pave the way for the use of SPR systems in the detection of electrical activity of biological cells

The effect of the potential on the surface plasmon resonance at a metal-liquid interface

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 50-51).Issued also on microfiche from Lange Micrographics.The resonance excitation of surface plasmons by a laser beam is highly sensitive to the dielectric properties of the media involved. In addition, the electromagnetic field is localized in the vicinity of a thin metal film which strongly enhances the observed physical effects as compared to measuring without surface plasmon resonance (SPR). In the traditional SPR sensing technique the variations of the refractive index of the sample medium induce changes in the angle of the resonance excitation, thus providing integrated information on the mass of the material present within the adsorption layer. This information is obtained by observing the SPR curve, namely by monitoring the minimum of the angular distribution of the reflected light. The influence of an electric potential applied to a gold film on the surface plasmon resonance phenomenon at the metal-liquid interface was studied. The oscillating shifts of the resonance angle and a gradual average drift were observed with a voltage cycling at different rates for various aqueous solutions as an adjacent medium. For the theoretical description, a model including redistribution of charges at the double layer near the interface and the oxidation of the gold film was developed. It was found that a change of the electronic density at voltages below the oxidation potential and, in addition, the oxidation of the gold surface above this threshold are the main mechanisms accounting for the observed experimental data

Dynamics on Spaces of Compact Subsets with Application to Brain Modeling

AbstractLetEbe an open, bounded subset ofRnand let P(E) be the collection of all subsets ofE. The theory of random sets deals with random processes whose outcomes are elements of P(E). Due to the infinite-dimensional nature of P(E), this theory is very technical. In this note we introduce a finite dimensional class of compact subsets ofE,Kn(E), which is dense in P(E) yet sufficiently rich for many applications.We study dynamical systems on the spaceKn(E) by considering transformations τ:Kn(E)→Kn(E) which are constructed from image source data such as occur in the dynamics of the brain. In particular, we establish sufficient conditions for the existence of invariant measures onKn(E). Under certain conditions these measures are absolutely continuous. We attempt to give meaning to the notion of expansiveness in brain dynamics