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F. Mauger 1, C. Chandre 1, T. Uzer 2 1 Centre de Physique Théorique, CNRS, Aix-Marseille Université 2 School of Physics, Georgia Institute of Technology.

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Presentation on theme: "F. Mauger 1, C. Chandre 1, T. Uzer 2 1 Centre de Physique Théorique, CNRS, Aix-Marseille Université 2 School of Physics, Georgia Institute of Technology."— Presentation transcript:

1 F. Mauger 1, C. Chandre 1, T. Uzer 2 1 Centre de Physique Théorique, CNRS, Aix-Marseille Université 2 School of Physics, Georgia Institute of Technology – Atlanta Financial support: PICS

2 Double ionization: the puzzling knee-shape Double Ionization SDI NSDI Linear polarization (LP) λ = 780 nm T = 100 fs (10 -13 s) May 11, 20112Strong field double ionization

3 ion detector electron detector  gain all information about the orbital  position of a molecule's atoms  observe attosecond dynamics http://hsb.uni-frankfurt.de/web/research/atomic/strongfields/press/ Web of science, topics: “nonsequential double ionization” COLTRIMS setup May 11, 20113Strong field double ionization Motivations

4 Classical mechanics: a knee He 2+ NS May 11, 2011 4 Strong field double ionization

5 Dynamics without the field 5 Chaotic motion organized by hyperbolic periodic orbits At any time it defines an inner and an outer electron May 11, 2011 Strong field double ionization

6 Reduced models for inner and outer electrons Outer electron Effective Hamiltonian Maximum return energy 3 step model (Corkum 1993) 1. ionization 2. return to the core 3. collision with the core electron Inner electron Effective Hamiltonian Laminar plot May 11, 20116Strong field double ionization

7 Double ionization: What is under the knee ? Double ionization: separate NSDI and SDI components. Complete SDI Maximum NSDI Equal sharing relation May 11, 20117Strong field double ionization

8 Linear polarization vs. circular polarization: “standard wisdom” “only a slight ellipticity of the laser polarization will ensure that the electron never returns to the environment of the ion” P. B. Corkum, PRL 71, 1994 (1993) “circular polarization suppresses the enhancement.” D.N. Fittinghoff et al., PRA 49, 2174 (1994) “enhanced double ionization for circular polarization contradicts simple rescattering theories” G. D. Gillen et al., PRA 64, 043413 (2001) “For a laser field with circular polarization and already a field with significant elliptical polarization (…) the recollision mechanism will lose its significance.” W. Becker and H. Rottke, Cont. Phys. 49, 199-223 (2008) “If the polarization is circular, then as soon as any portion of the wavepacket emerges from the atom (…) the motion ensures that the wavepacket never returns to the ion of its birth” P.B. Corkum, Physics Today (March 2011) May 11, 2011 Linear polarization Circular polarization 8Strong field double ionization

9 Circular polarization: no knee ? Experimental results (CP) May 11, 20119Strong field double ionization

10 Observation of a knee for Mg no knee for He significant amount of recollision for Mg. for He, recollision suppressed because of initial conditions. Mg 2+ He 2+ Numerical simulations (CP) May 11, 201110Strong field double ionization NSDI with circular polarization

11 Circular polarization: insight from nonlinear dynamics We observe a knee shape with Mg Even with CP we get a significant amount of recollisions Canonical transformation into a rotating frame  Time independent laser field  Saddle point which controls both ionization and recollision  Zero velocity surface May 11, 201111Strong field double ionization

12 LP  inner/outer electrons  reduced models  predictions on the knee  symplectic map for recollision dynamics CP  conditions for knee in CP  agreement with experiments  modified recollision scenario May 11, 201112Strong field double ionization Physical Review Letters 105,083002 (2010) Actualités de l’INP-CNRS: http://www.cnrs.fr/inp/spip.php?article377 Conclusions/Perspectives


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