Biomedical subjects

K Le Guen

Publications and source records attributed to K Le Guen.

4 recordsLinked to original sources

PubMed2005

Photofragmentation study of hexamethyldisiloxane following core ionization and direct double ionization.

X-ray photoelectron spectroscopy and Auger spectroscopy studies of gas-phase hexamethyldisiloxane (HMDSO) are presented. The photodissociation of this molecule is studied using various experimental coincidence techniques. We compare the fragmentation pathways observed after core ionization followed by Auger decay and after valence double photoionization of the molecule. A strongly selective production of the doubly charged tetramethyldisiloxane ion is observed in the low binding-energy regions. Theoretical calculations are carried out to tentatively explain the stability of the produced dication.

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PubMed2005

Influence of formation path on the CH2BrCl2+ dissociation dynamics.

To get further insight into the CH2BrCl site-selective fragmentation previously observed upon inner-shell ionization, we have performed high-resolution Br 3d and Cl 2p Auger and spin-orbit resolved Br 3d Auger spectra, and studied the dissociation properties of the CH2BrCl2+ dication formed at threshold by means of threshold electron pair-ion coincidence measurements. The key point is that the origin of site-specific bond breaking is found in the Auger decay itself, as it preferentially populates selected dication states. Whereas the predominance of the C-Br bond breaking is observed in both threshold and inner-shell studies, no signature of selective C-Cl rupture is reported for the dication formed at threshold.

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PubMed2002

Nondipolar electron angular distributions from fixed-in-space molecules.

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N (2). Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.

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PubMed2001

Dynamical angular correlation in molecular Auger decay.

The first measurements of the angular distribution of Auger electrons from fixed-in-space molecules have been performed in the C K-shell ionization region of CO, for both parallel and perpendicular orientations of the molecular axis with respect to the light polarization vector. The angular distributions obtained for the CO(2+)B(1)Sigma Auger final state show dramatic spectral variations, which also depend on the initial ionization channels, Sigma or Pi, and on the ionization photon energy. This dynamical angular correlation process strongly suggests the breakdown of a two-step model in which the Auger decay is treated independently of the initial photoionization process.

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