Dresden 2011 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 1: Interaction with VUV and X-ray light (FEL) I
A 1.4: Vortrag
Montag, 14. März 2011, 12:00–12:15, BAR 205
Nonlinear atomic response to ultraintense and ultrashort x-ray pulses — Gilles Doumy1,2, C. Roedig1, •Sang-Kil Son3, C. Blaga1, A. DiChiara1, A. Agostini1, L.F. DiMauro1, R. Santra3,4, N. Berrah5, C. Bostedt6, J.D. Bozek6, P.H. Bucksbaum7, J. Cryan7, L. Fang5, S. Ghimire7, M.J. Glownia7, M. Hoener5, E.P. Kanter2, B. Krässig2, M. Messerschmidt6, D. Reis7, N. Rohringer8, and L. Young2 — 1The Ohio State University, USA — 2Argonne National Laboratory, USA — 3Center for Free-Electron Laser Science, DESY, Germany — 4University of Hamburg, Germany — 5Western Michigan University, USA — 6Linac Coherent Light Source, SLAC National Accelerator Laboratory, USA — 7PULSE Institute, SLAC National Accelerator Laboratory, USA — 8Lawrence Livermore National Laboratory, USA
The nonlinear response of neon atoms to ultraintense, ultrashort x-ray pulses is investigated with the LCLS x-ray free-electron laser. The production of Ne9+ is observed at kilovolt x-ray photon energies below the absorption edge of the Ne8+ ground state and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of direct 2-photon ionization of the Ne8+ ground state and a high-order sequential process involving two 1-photon ionization processes via transient excited states on a time scale faster than the Auger decay. We find that the nonlinear 2-photon ionization cross section is orders of magnitude larger than expected.