photo credits: Lionel Windels

photo credits: Lionel Windels

Ultrashort X-Rays for Atmospheric and Biological Dynamics

Since late 2015 and in close collaboration with ETH Ultrafast Spectroscopy and Attosecond Science laboratory trough the NCCR MUST project, we develop an ultrashort X-Ray laser beam using High Harmonic Generation.

We intend to use Femtosecond Time resolved X ray spectroscopy in the water window to investigate fundamental questions related to physical chemistry. We plan to expand on the first successfull results and observe the charge/energy transfer dynamics in solids, nanoparticles, and liquids. We are actively working for implemeting broadened pulse compression and CEP stabilization to attain attosecond pulses throughout the water
window.

HHG setup
Soft-X-ray transient-absorption spectroscopy with a high-harmonic source A)Experimental setup, B) High-harmonic spectrum at the carbon K-edge and transmitted spectrumthrough CF4 gas, C) High-harmonic spectrum at the sulfur L-edges and transmitted spectrumthrough SF6 gas.

Main result

In 2016 with the group of H.J Woerner, we observed the reaction dynamics of photoexcited molecules (CF 4 and SF 6) by transient-Xray absorption spectroscopy using a HHG source in the water window [1]. The source is based on a few cycle 1.8 um laser driven HHG in neon up to 350 eV. By probing element-specific core-to- valence transitions at the carbon K-edge or the sulfur L-edges, we characterized their reaction paths and observe the effect of symmetry breaking through the splitting of absorption bands and Rydberg-valence mixing induced by the geometry changes. The timescale over which the process occurs is shorter than 40 fs. Ab-initio calculations have been performed to confirm the relaxation pathways. The ionization-induced fragmentation dynamics of SF 6 in SF 5 + was uncovered as well, observed on the L-edges absorption of the Sulphur atom.


1. Y. Pertot, C. Schmidt, M. Matthews, A. Chauvet, M. Huppert, V. Svoboda, A. von Conta, A. Tehlar, D. Baykusheva,
J.-P. Wolf, H. J. W├Ârner
"Time-resolved x-ray absorption spectroscopy with a water window high-harmonic source"
Science 355(6322), 264-267 (2017)
doi: 10.1126/science.aah6114