Hannover 2013 – scientific programme

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A: Fachverband Atomphysik

A 7: Interaction with VUV and X-ray light I

A 7.4: Talk

Monday, March 18, 2013, 14:45–15:00, B 302

Attosecond-resolved electron dynamics around the 1st ionization threshold of helium measured by multidimensional absorption spectroscopy — •Andreas Kaldun, Christian Ott, Veit Stooss, Philipp Raith, Kristina Meyer, Martin Laux, Alexander Blaettermann, Thomas Ding, and Thomas Pfeifer — Max-Planck Institut f. Kernphysik, Heidelberg, Germany

We recently developed a transient-coupling measurement scheme, which we employed to uncover coherent laser-induced coupling of doubly-excited helium states to continuum states [1]. Here, we apply this measurement scheme to study in detail the coherent electron dynamics and general absorption phenomena arising for single-excitation of helium around 24 eV with attosecond-pulsed VUV light fields. Exploiting a multidimensional control by (a) varying the time delay between the attosecond and a coupling laser pulse, (b) tuning the coupling laser intensity and (c) analyzing the propagation direction of the transmitted VUV attosecond pulse we observe the transformation of the original (Lorentzian) resonance shapes into Fano line shapes. To understand the mechanism behind this quantum control we performed numerical simulations to model our experimental results, which include the attosecond-pulsed excitation and laser coupling of multiple excited states [2]. These simulations allowed us to identify the ponderomotive dressing of the states in the laser field as a key component for understanding the control of several line shapes of the observed absorption spectra. [1]C. Ott et al., arXiv:1205.0519v1 [physics.atom-ph] (2012) [2]A. Kaldun et al., in preparation (2013)