Storage ring method

We will be rather brief in describing the principles of the experimental methods that are most commonly used in studies of dissociative recombination, afterglows and colliding beams (merged beams and ion storage rings). It should suffice to recount some of their generic properties. 

The SEXAFS teehnique is a partieular surface sensitive detection mode applied to an EXAFS measurement, performed in a particular environment, the Ultra High Vacuum, which is needed in order to prepare and protect the atomic-scale eleanliness of surface and interface systems for the whole time length of the experiment. As such the technique borrows equipment and procedures from the surface science spectroscopies, and exploitation procedures of the synchrotron radiation source from the conventional, non vacuum, EXAFS method. The studies described below have been performed at the Laboratoire pour T Utilisation du Rayonnement Electro-magnetique (LURE) exploiting synehrotron radiation from the storage ring DCI... 

For a somewhat more accurate estimate of the apparent source size in particular emission and observation conditions, numerical methods of Fourier optics can be used. In this framework, the effective source size can be obtained either by backpropagation of the wavefront (at a specific wavenumber) to the source position, or by simulating the radiation focusing at optical magnification equal to 1. To illustrate this, we have considered two cases an IR beamline at the NSLS (0.8 GeV storage ring) normalized at 1000 mA (electron source size = 550 p,m horizontal, 70 (im vertical) and an IR beamline at SOFFIT, (2.75 GeV - electron source... 

Synchrotron storage rings, for instance, are able to provide an extremely high flux of nearly monochromatic X-radiation on a small sample area. They could form the basis of XRF set-ups and enhance other microana-lytical methods to provide accurate determinations. In the future they could serve as a reference method for elemental trace analysis on the microscopical level (with the quality of the random number generator, a non-SI concept, as the prime source of error). 

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