Berlin 2014 – scientific programme

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A: Fachverband Atomphysik

A 15: Poster: Interaction with strong or short laser pulses

A 15.4: Poster

Monday, March 17, 2014, 16:30–18:30, Spree-Palais

Line shape modifications of singly-excited Helium states coupled to a ponderomotive continuum — •Veit Stooß, Andreas Kaldun, Christian Ott, and Thomas Pfeifer — Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany

In order to understand and control the dynamics of correlated electron systems as they appear in atoms and molecules it is instructive to study the most fundamental case, namely two interacting electrons bound to an atom. Here, we investigate the special case of singly-excited states in Helium and their laser coupling to a ponderomotive continuum. The line shapes observed in attosecond transient absorption spectra reveal signatures of both bound-to-continuum and bound-to-bound laser coupling. To better understand the full laser coupling dynamics a model simulation was carried out in which the states of the system are excited by an extreme ultraviolet (XUV) laser pulse and coupled by a femtosecond infrared (IR) pulse. The simulation includes the s-, p-, and d-series of singly-excited helium. The completed simulation allows for varying the infrared intensity of the coupling pulse or the relative time delay between XUV- and IR-pulse as control parameters. In addition the coupling between the states as well as the coupling to the continuum can be activated separately to study the relative contributions of the different coupling channels. The results are discussed within the recently developed Fano-phase formalism [1] which shows that resonance line shapes can be used to extract the laser intensity. [1] C. Ott et al., Science 340, 716 (2013)