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Femtosecond Soft-X-ray Absorption Spectroscopy of Liquids with a Water-Window High-Harmonic Source

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posted on 2020-02-26, 22:46 authored by Adam D. Smith, Tadas Balčiu̅nas, Yi-Ping Chang, Cédric Schmidt, Kristina Zinchenko, Fernanda B. Nunes, Emanuele Rossi, Vít Svoboda, Zhong Yin, Jean-Pierre Wolf, Hans Jakob Wörner
Femtosecond X-ray absorption spectroscopy (XAS) is a powerful method to investigate the dynamical behavior of a system after photoabsorption in real time. So far, the application of this technique has remained limited to large-scale facilities, such as femtosliced synchrotrons and free-electron lasers (FEL). In this work, we demonstrate femtosecond time-resolved soft-X-ray absorption spectroscopy of liquid samples by combining a sub-micrometer-thin flat liquid jet with a high-harmonic tabletop source covering the entire water-window range (284–538 eV). Our work represents the first extension of tabletop XAS to the oxygen edge of a chemical sample in the liquid phase. In the time domain, our measurements resolve the gradual appearance of absorption features below the carbon K-edge of ethanol and methanol during strong-field ionization and trace the valence-shell ionization dynamics of the liquid alcohols with a temporal resolution of ∼30 fs. This technique opens unique opportunities to study molecular dynamics of chemical systems in the liquid phase with elemental, orbital, and site sensitivity.

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