Femtosecond soft–X–Ray absorption spectroscopy of liquids with a water-window high-harmonic source

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 table–top source covering the entire water-window range (284 - 538 eV). Our work represents the first extension of table-top 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, which trace the valence-shell ionization dynamics of the liquid alcohols with a temporal resolution of ~30 fs.