title: Extracting phase and amplitude modifications of laser-coupled Fano resonances.
abstract: Fano line shapes observed in absorption spectra encode information on the amplitude and phase of the optical dipole response. A change in the Fano line shape, e.g., by interaction with short-pulsed laser fields, allows us to extract dynamical modifications of the amplitude and phase of the coupled excited quantum states. We introduce and apply this physical mechanism to near-resonantly coupled doubly excited states in helium. This general approach provides a physical understanding of the laser-induced spectral shift of absorption-line maxima on a sub-laser-cycle time scale as they are ubiquitously observed in attosecond transient-absorption measurements.
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kaldun
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ott
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Blättermann
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Laux
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Meyer
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ding
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pfeifer