TY  - JOUR
AU  - Stransky, Michal
AU  - Lane, Thomas
AU  - Gorel, Alexander
AU  - Boutet, Sebastien
AU  - Schlichting, Ilme
AU  - Mancuso, Adrian
AU  - Jurek, Zoltan
AU  - Ziaja, Beata
TI  - Ionization by XFEL radiation produces distinct structure in liquid water
JO  - Communications Physics
VL  - 7
IS  - 1
SN  - 2399-3650
CY  - London
PB  - Springer Nature
M1  - PUBDB-2024-01036
SP  - 281
PY  - 2024
AB  - In the warm dense matter (WDM) regime, where condensed, gas, and plasma phases coexist, matter frequently exhibits unusual properties that cannot be described by contemporary theory. Experiments reporting phenomena in WDM are therefore of interest to advance our physical understanding of this regime, which is found in dwarf stars, giant planets, and fusion ignition experiments. Using 7.1 keV X-ray free electron laser radiation (nominally 5×105 J/cm<sup>2</sup>), we produced and probed transient WDM in liquid water. Wide-angle X-ray scattering (WAXS) from the probe reveals a new  9 Å structure that forms within 75 fs. By 100 fs, the WAXS peak corresponding to this new structure is of comparable magnitude to the ambient water peak, which is attenuated. Simulations suggest that the experiment probes a superposition of two regimes. In the first, fluences expected at the focus severely ionize the water, which becomes effectively transparent to the probe. In the second, out-of-focus pump radiation produces O<sup>1+</sup> and O<sup>2+</sup> ions, which rearrange due to Coulombic repulsion over 10 s of fs. Our simulations account for a decrease in ambient water signal and an increase in low-angle X-ray scattering but not the experimentally observed 9 Å feature, presenting a new challenge for theory. 
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:001295013200001
DO  - DOI:10.1038/s42005-024-01768-6
UR  - https://bib-pubdb1.desy.de/record/604238
ER  -