Mercredi 15 mars à 11h00,
Salle Louis Weil, E424
Orateur : Alexander von Reppert (Institut of Physics and Astronomy, University of Postdam, Germany)
"Time-resolved X-Ray Diffraction as a Tool to Probe Non-Equilibrium States of Crystalline Matter"
This talk aims at providing an introduction to the possibilities of ultrafast X-Ray diffraction (UXRD) based on the laser pump – X-Ray probe technique. I will focus my presentation on results obtained at a Plasma X-ray source setup  which provides approximately 250fs long hard X-Ray bursts. A brief comparison of the laboratory based measurements to diffraction experiments at synchrotron facilities is provided to show the common and complementary aspects of both setups.
Two results are presented in the second part of the talk :
1) UXRD has recently enabled us to observe the vibration and cooling of ultrathin gold nanotriangles after laser excitation .
2) A systematic study of the lattice dynamics in antiferromagnetic Holmium and Dysprosium thin films indicates a long lasting non-equilibrium between spin an phonon systems in these strongly magnetostrictive rare earth films  as well as a reduced heat transport through magnetic layers .
 D. Schick et al. Journal of Applied Crystallography, vol. 46, pp. 1372–1377, (2013)
 A. von Reppert et al. The Journal of Physical Chemistry C 120.50 pp. 28894-28899, (2016)
 A. von Reppert et al. Structural Dynamics 3.5 : 054302, (2016)
 A. Koc et al. arXiv preprint arXiv:1701.05918 (2017)