REACTIVITE SOUS RAYONNEMENT D'ESPECES EN PHASE DILUEE

HAXPES : Hard X-ray PhotoElectron Spectroscopy.

Hard x-ray photoelectron spectroscopy is the novel extension to high kinetic energies photoemission, a spectroscopic technique extremely well established as a powerful probe of the electronic properties in materials and gas phases. This apparatus can be used with solid state sample as well as with gases. This project has received an ANR grant (Marc Simon responsible). The apparatus is a permanent endstation of the GALAXIES beamline. For gas phase studies, this apparatus is unique in the world.

The detail of the apparatus has been published (http://www.sciencedirect.com/science/article/pii/S036820481300008X). Briefly, it consist of an hemispherical electron analyzer, a solid state sample holder and a gas cell. In principle, a resolution of 35 meV for electrons up to 10 keV of kinetic energies can be achieved. Thanks to a High Resolution Monochromator, the photon bandwidth will be soon equal to 100 meV in the whole photon energy range of the GALAXIES beamline (between 2.3 and 13.5 keV).

This project allows to study sub-femtosecond dynamics of molecular deformation in the gas phase. A detailed description of the dynamics of the excited systems in the very first hundreds of attoseconds is essential to understand and potentially control the formation of the final fragment products. Excitations of short-lived core-levels are more prompt to yield relevant information on ultra-fast nuclear motion. The first results obtained on the CH3Cl molecule have been published (science direct…).

Due to the momentum conservation, photoionization of an atom at high photon energy leads to a strong translational recoil. The Auger electron happening after inner shell photoionization carries the information of this recoil effect and a Doppler shift has been measured in the case of the inner shell photoionisation of the neon atom (science direct…). In case of the photoionization of a molecule at high photon energy, translational, vibrational and rotational recoil are observed. We have studied the Doppler effect occuring on the CO molecule.

The high resolution capabilities of the HAXPES setup have been used to measure the recoil effect in the photoionization process directly on the measurement of the photoelectron. Some preliminary data have been obtained on the CO molecule.

The spectroscopy of double core hole (DCH) Atoms and Molecules has the great advantage to be much more sensitive to the chemical environment than the traditional ESCA. In order to get access to its spectroscopy with the detection of only one electron, it is possible to record the structures of the DCH with one electron in the empty orbitals instead of the continuum. Thanks to its high photon flux and high resolution, the HAXPES setup is particularly well suited for this kind of studies.


Dernière modification : January 12 2015 17:27:04.