Seminários

Seminário Extraordinário

Teremos no dia 19/07, as 11:00 na sala 201 do Instituto de Física, o seminário do Dr. Laurent Nahon, intitulado "Performances and recent scientific results obtained on DESIRS : a VUV high resolution variable polarization beamline @ SOLEIL for dichroism and spectroscopy".

O Dr. Nahon é o responsável pala linha DESIRS, no síncrotron SOLEIL, Franca. Neste seminário serão apresentadas as vantagens da linha de luz assim como os resultados mais marcantes obtidos nesta linha.

Título: Performances and recent scientific results obtained on DESIRS : a VUV high resolution variable polarization beamline @ SOLEIL for dichroism and spectroscopy

Palestrante: Laurent Nahon (SOLEIL, St Aubin)

Resumo:

Under operation since 2008, DESIRS is an undulator-based beamline covering the VUV range (5-
40 eV) mainly targeting gas phase samples, as well as amino-acids in the condensed matter. Its
scientific case, based upon photon excitations in the valence and inner-valence shell is five-fold :
1. High resolution spectroscopy on small molecular systems, mainly of astrophysics interest
2. Spectroscopy, fragmentation and reactivity of energy-selected cations and mass
spectrometry  
3. Photoionization dynamics (clusters and laser-excited systems)
4. Alignment, vectorial correlation and chirality
5. Excitation and relaxation in the condensed matter
In order to fulfill such a program, one needs harmonic-free, high flux, high resolution and variable
polarization photons.  
The photon source is a 10 m-long electromagnetic fully variable polarization undulator whose
polarization has been fully measured and calibrated (in the linear and circular modes) with a home-
made VUV polarimeter.1  
This pseudo white beam enters then either the high resolution Fourier-Transform Spectroscopy
(FTS) branch, equipped with a windowless gas cell and a free molecular beam, for absorption
experiments with an unprecedented resolving power close to 106,2 or the monochromator branch,
with a state-of-the-art resolving power in the 105-2.105 range, for all types of spectroscopies. This
latter branch is connected to the multipurpose molecular beam chamber SAPHIRS, equipped with a
new electron/ion imaging coincidence spectrometer (DELICIOUS2) allowing to perform AR-PES
and ion imaging on mass-selected compounds as well as TPES and TPEPICO with sub-meV
resolutions.3
After a short introduction to SOLEIL, the DESIRS scientific case and the beamline and associated
endstations performances will be presented. Then, I will describe some recent results including the
Photoelectron Circular Dichroism (PECD) observed by imaging techniques upon photoionization of
chiral systems with Circularly-Polarized VUV light,4 with future prospects on amino-acids as
produced in the gas phase by thermodesorption of bio-aerosols,5 as well as asymmetric
photosynthesis of amino-acids from interstellar ice analogs.6


1 L. Nahon and C. Alcaraz, Applied Optics 43, 1024 (2004).
2 N. de Oliveira, M. Roudjane, D. Joyeux, D. Phalippou, J. C. Rodier, and L. Nahon, Nature Photonics    
5, 149 (2011).
3 G. Garcia, H. Soldi-Lose, and L. Nahon, Rev. Sci. Inst. 80, 023102 (2009).
4 L. Nahon, G. Garcia, H. Soldi-Lose, S. Daly, and I. Powis, Phys. Rev. A 82, 032514 (2010).
5 F. Gaie-Levrel, G. Garcia, M. Schwell, and L. Nahon, Phys. Chem. Chem. Phys. 13, 7024 (2011).
6 P. de Marcellus, C. Meinert, M. Nuevo, J.-J. Filippi, G. Danger, D. Deboffle, L. Nahon, L. Le  
Sergeant d'Hendecourt, and U. J. Meierhenrich, Astrophysical Journal letters 727, L27 (2011).