Hamburg 2009 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 11: Attosecond Physics I

A 11.5: Vortrag

Dienstag, 3. März 2009, 15:30–15:45, VMP 6 HS-B

Molecular orbital tomography using HHG and ATI — •Elmar van der Zwan, Ciprian Chirila, and Manfred Lein — Institute for Physics, University of Kassel, Germany

In 2004 a revolutionary method to perform tomographic imaging of molecular orbitals using high-harmonic generation (HHG) caught a lot of attention [1]. The method is based on the simplification that the returning electron in the three-step model can be modeled as a plane wave. We have shown that orbitals of arbitrary symmetry can be reconstructed if one uses extremely short laser pulses that ensure the continuum wave packet recombines from one side only [2]. Within the single-active-electron approximation, the challenge of the scheme lies in the accurate determination of the continuum wave packet. For a known orbital, an expression for the continuum wave packet in terms of classical trajectories is derived from the Lewenstein model. We propose an experimentally feasible method to determine the composition of the continuum wave packet using both HHG and angularly resolved above-threshold ionization (ATI) electrons. By incorporating the ATI electrons in the procedure, the instantaneous tunneling rates for electron emission parallel to the applied field can be measured. This avoids one of the major assumptions in the tomographic scheme, namely approximating the tunnel ionization of the molecule by that of the reference.

[1] Itatani et al. Nature 432, 867-871 (2004)

[2] van der Zwan et al. Phys. Rev. A 78, 033410 (2008)