title: Time-resolved four-wave-mixing spectroscopy for inner-valence transitions.
abstract: Noncollinear four-wave-mixing (FWM) techniques at near-infrared (NIR), visible, and ultraviolet frequencies have been widely used to map vibrational and electronic couplings, typically in complex molecules. However, correlations between spatially localized inner-valence transitions among different sites of a molecule in the extreme ultraviolet (XUV) spectral range have not been observed yet. As an experimental step toward this goal, we perform time-resolved FWM spectroscopy with femtosecond NIR and attosecond XUV pulses. The first two pulses (XUV-NIR) coincide in time and act as coherent excitation fields, while the third pulse (NIR) acts as a probe. As a first application, we show how coupling dynamics between odd- and even-parity, inner-valence excited states of neon can be revealed using a two-dimensional spectral representation. Experimentally obtained results are found to be in good agreement with ab initio time-dependent R-matrix calculations providing the full description of multielectron interactions, as well as few-level model simulations. Future applications of this method also include site-specific probing of electronic processes in molecules.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ding
authors.forename: Christian
authors.initials: C
authors.lastname: Ott
authors.forename: Andreas
authors.initials: A
authors.lastname: Kaldun
authors.forename: Alexander
authors.initials: A
authors.lastname: Blättermann
authors.forename: Kristina
authors.initials: K
authors.lastname: Meyer
authors.forename: Veit
authors.initials: V
authors.lastname: Stooss
authors.forename: Marc
authors.initials: M
authors.lastname: Rebholz
authors.forename: Paul
authors.initials: P
authors.lastname: Birk
authors.forename: Maximilian
authors.initials: M
authors.lastname: Hartmann
authors.forename: Andrew
authors.initials: A
authors.lastname: Brown
authors.forename: Hugo
authors.initials: H
authors.lastname: Van Der Hart
authors.forename: Thomas
authors.initials: T
authors.lastname: Pfeifer