3 research outputs found
Time-resolved four-wave-mixing spectroscopy for inner-valence transitions
Non-collinear 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 towards 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
multi-electron interactions, as well as few-level model simulations. Future
applications of this method also include site-specific probing of electronic
processes in molecules.Comment: 5 pages, 3 figure
All-XUV Pump-Probe Transient Absorption Spectroscopy of the Structural Molecular Dynamics of Di-iodomethane
In this work, we use an extreme-ultraviolet (XUV) free-electron laser (FEL) to resonantly excite the I: 4 transition of a gas-phase di-iodomethane (CHI) target. This site-specific excitation generates a 4 core hole located at an iodine site, which leaves the molecule in a well-defined excited state. We subsequently measure the time-dependent absorption change of the molecule with the FEL probe spectrum centered on the same I: 4 resonance. Using ab initio calculations of absorption spectra of a transient isomerization pathway observed in earlier studies, our time-resolved measurements allow us to assign the timescales of the previously reported direct and indirect dissociation pathways. The presented method is thus sensitive to excited-state molecular geometries in a time-resolved manner, following a core-resonant site-specific trigger