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PLEIADES keeps its promise
SOLEIL Company Contents > All the news > News 2009 > PLEIADES
The first electron spectra were recorded on PLEIADES the night of May 23rd, 2009. These testified to the exceptional possibilities offered by this beamline to those interested in the study of dilute matter using inner shell spectroscopy. Welcome to the ultra high resolution chemical physics.

PLEIADES is an ultra high resolution soft X-ray beamline (ultimate resolving power of approximately 100000 at 50 eV) covering the spectral region between 7 eV and 1 keV thanks to the use of two undulator sources. This beamline, which will be available to users on a permanent basis for the next call for beamtime applications in September 2009, is dedicated to physicochemical spectroscopy studies of dilute matter (atoms, molecules, ions, clusters, biological molecules and nanoparticles).
For this type of study, the advantage of this high spectral resolution lies in the possibility of exploring the dynamics of atomic nuclei and its interplay with the electronic decay over very short time scales in the order of femtoseconds (10-15 sec).

During the last run, after almost two weeks of adjustments and bug fixing, the PLEIADES group collected the very first electron spectra of this beamline in the sublifetime regime: it was over the weekend of the 23rd-24th May that the resonant Auger-Raman decay spectra of krypton (Kr 3d5/2→5p) and nitrogen (N1s→π*), below, were recorded.


The sharpness and detail of the peaks augur well for more spectacular performances in accessing fast nuclear dynamics induced by inner-shell excitation. This choice of very high resolution and the latest technology that makes this possible (see insert) already seems to be living up to expectations. Advanced test phases of the beamline programmed for next July will be able to show what the beamline capabilities are not only in terms of resolution but also photon flux. A combination of ultra-high resolution and high photon flux will make it possible to tackle systems with greater complexity than molecules and to study, for example, isolated nanoparticles, atomic and molecular clusters or large molecules of biological interest.

The first holographic gratings with 2400 lines/mm

Resulting from a close collaboration between SOLEIL and HORIBA Jobin Yvon, the gratings with varied groove depth (VGD) are holographic gratings produced by ion beam milling, where the depth of groove varies regularly along the lines. When the grating is illuminated by a very narrow beam, a simple translation in the direction of the lines allows the blaze condition* to be continuously adjusted by selecting the depth of groove adapted to the conditions of use. These VGD gratings have been designed specifically for the new generation of synchrotrons: the low beam divergence of the latest synchrotron beamlines, together with the tuning possibilities specific to these new gratings, offer a unique opportunity for continuously maintaining the blaze condition and therefore keeping optimal measurement performance over the whole spectrum with just one grating. Most monochromators that equip the XUV beamlines at SOLEIL synchrotron (TEMPO, CASSIOPEE, ANTARES) were designed to use these gratings. As for the PLEIADES monochromator, it is equipped with the first highly dispersive grating with as many as 2400 lines/mm, which allows it to reach the ultimate resolutions for which the beamline was designed.

*The blaze condition is the configuration used to maximize the diffraction intensity.
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