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Transcript of F. Mauger 1, C. Chandre 1, T. Uzer 2 1 Centre de Physique Théorique, CNRS, Aix-Marseille...
Strong field double ionization: Insight from non-linear dynamics
F. Mauger1, C. Chandre1 , T. Uzer2
1Centre de Physique Théorique, CNRS, Aix-Marseille Université2School of Physics, Georgia Institute of Technology – Atlanta
Financial support:
PICS
Double ionization: the puzzling knee-shape
Double IonizationSDI
NSDI
Linear polarization (LP)λ = 780 nmT = 100 fs (10-13 s)
Experimental dataWalker et al (1994)
May 11, 2011 2Strong field double ionization
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, 2011 3Strong field double ionization
Motivations
Classical mechanics: a knee
He2+
NS
May 11, 2011 4Strong field double ionization
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, 2011Strong field double ionization
Reduced models for inner and outer electrons
Outer electron Effective Hamiltonian
Maximum return energy
3 step model (Corkum 1993)1. ionization2. return to the core3. collision with the core electron
Inner electron Effective Hamiltonian
Laminar plot
May 11, 2011 6Strong field double ionization
Double ionization: What is under the knee ?
Double ionization: separate NSDI and SDI components.
Complete SDI
Maximum NSDIEqual sharing
relation
May 11, 2011 7Strong field double ionization
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
Circular polarization: no knee ?
Experimental results (CP)
Gillen et al (2001)Fittinghoff et al (1994)
contradiction?
May 11, 2011 9Strong field double ionization
Observation of a knee for Mg no knee for He significant amount of recollision
for Mg. for He, recollision suppressed
because of initial conditions.
Mg2+
He2+
Numerical simulations (CP)
May 11, 2011 10Strong field double ionization
NSDI with circular polarization
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, 2011 11Strong field double ionization
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, 2011 12Strong field double ionization
Physical Review Letters 105,083002 (2010)
Actualités de l’INP-CNRS: http://www.cnrs.fr/inp/spip.php?article377
Conclusions/Perspectives