title: Lorentz meets Fano in spectral line shapes: a universal phase and its laser control.
abstract: Symmetric Lorentzian and asymmetric Fano line shapes are fundamental spectroscopic signatures that quantify the structural and dynamical properties of nuclei, atoms, molecules, and solids. This study introduces a universal temporal-phase formalism, mapping the Fano asymmetry parameter q to a phase φ of the time-dependent dipole response function. The formalism is confirmed experimentally by laser-transforming Fano absorption lines of autoionizing helium into Lorentzian lines after attosecond-pulsed excitation. We also demonstrate the inverse, the transformation of a naturally Lorentzian line into a Fano profile. A further application of this formalism uses quantum-phase control to amplify extreme-ultraviolet light resonantly interacting with He atoms. The quantum phase of excited states and its response to interactions can thus be extracted from line-shape analysis, with applications in many branches of spectroscopy.
authors: Max-Planck-Institut für Kernphysik, Heidelberg, Germany.
authors: Christian
authors: C
authors: Ott
authors: Andreas
authors: A
authors: Kaldun
authors: Philipp
authors: P
authors: Raith
authors: Kristina
authors: K
authors: Meyer
authors: Martin
authors: M
authors: Laux
authors: Jörg
authors: J
authors: Evers
authors: Christoph H
authors: CH
authors: Keitel
authors: Chris H
authors: CH
authors: Greene
authors: Thomas
authors: T
authors: Pfeifer