Speaker
Description
Soft-X-ray attosecond spectroscopy at FELs provides direct access to ultrafast electronic dynamics in matter with simultaneous sub-femtosecond resolution and atomic-site specificity*. By exploiting core-level transitions, these approaches offer a localized and phase-sensitive probe of electronic coherence, extending attosecond science beyond valence dynamics into the regime of strongly correlated, site-selective excitation.
The high-repetition-rate operation of LCLS-II delivers the photon flux and peak intensity required to both initiate and resolve coherent motion of deeply bound electrons. Crucially, FELs uniquely enable attosecond pump–attosecond probe schemes at core-level energies, allowing the preparation and interrogation of non-stationary electronic states at the ultimate time resolution of molecular processes**.
Our two recent experimental user campaigns explored the creation, evolution, and decay of core-hole coherence in molecular systems, ranging from small molecules to transition-metal complexes. These attosecond pump–probe measurements reveal how quantum coherence emerges from core-excitation and how this coherence is subsequently reshaped by electron–nuclear coupling on few-femtosecond timescales.
Together, these results establish soft-X-ray attosecond spectroscopy at FELs as a uniquely powerful approach to initiate, control, and resolve electron dynamics in complex matter, defining a new experimental regime for ultrafast molecular science.
Funding Agency
This work was supported by the U.S. Department of Energy, Office of Science, Office of
Basic Energy Sciences under Contract No. DE-AC02-
76SF00515 and ETH Zurich.
Footnotes
- Driver, T. et al. Attosecond Coherent Electron Motion in a Photoionized Aromatic Molecule. arXiv:2411.01700
** Guo, Z., Driver, T., Beauvarlet, S. et al. Experimental demonstration of attosecond pump–probe spectroscopy with an X-ray free-electron laser. Nat. Photon. 18, 691–697 (2024). https://doi.org/10.1038/s41566-024-01419-w
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