Attosecond-pump attosecond-probe x-ray spectroscopy of liquid water
Shuai Li, Lixin Lu, Swarnendu Bhattacharyya, Carolyn I. Pearce, Kai Ming Li, Emily T. Nienhuis, Gilles Doumy, Richard D. Schaller, Stefan Moeller, Ming‐Fu Lin, Georgi L. Dakovski, David J. Hoffman, Douglas Garratt, Kirk A. Larsen, J. D. Koralek, Christina Y. Hampton, David Cesar, Joseph Duris, Zhen Zhang, Nicholas Sudar, James Cryan, Agostino Marinelli, Xiaosong Li, Ludger Inhester, Robin Santra, Linda Young
Abstract
Attosecond-pump/attosecond-probe experiments have long been sought as the most straightforward method for observing electron dynamics in real time. Although there has been much success with overlapped near-infrared femtosecond and extreme ultraviolet attosecond pulses combined with theory, true attosecond-pump/attosecond-probe experiments have been limited. We used a synchronized attosecond x-ray pulse pair from an x-ray free-electron laser to study the electronic response to valence ionization in liquid water through all x-ray attosecond transient absorption spectroscopy (AX-ATAS). Our analysis showed that the AX-ATAS response is confined to the subfemtosecond timescale, eliminating any hydrogen atom motion and demonstrating experimentally that the 1b 1 splitting in the x-ray emission spectrum is related to dynamics and is not evidence of two structural motifs in ambient liquid water.