Distinct transient structural rearrangement of ionized water revealed by XFEL X-ray pump X-ray probe experiment
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arXiv
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| Autori principali: | , , , , , , , |
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| Natura: | Preprint |
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2024
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| _version_ | 1866910334207393792 |
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| author | Stransky, Michal Lane, Thomas J. Gorel, Alexander Boutet, Sébastien Schlichting, Ilme Mancuso, Adrian P. Jurek, Zoltan Ziaja, Beata |
| author_facet | Stransky, Michal Lane, Thomas J. Gorel, Alexander Boutet, Sébastien Schlichting, Ilme Mancuso, Adrian P. Jurek, Zoltan Ziaja, Beata |
| contents | Using X-ray free electron laser (XFEL) radiation to conduct an X-ray pump X-ray probe experiment, we studied strongly ionized water as part of our ongoing work on radiation damage. After irradiance with a pump pulse with a nominal fluence of ~$5 \times 10^5$ J/cm$^2$, we observed for pump-probe delays of 75 fs and longer an unexpected structural rearrangement, exhibiting a characteristic length scale of ~9 Å. Simulations suggest that the experiment probes a superposition of ionized water in two distinct regimes. In the first, fluences expected at the X-ray focus create nearly completely ionized water, which as a result becomes effectively transparent to the probe. In the second regime, out of focus pump radiation produces O$^{1+}$ and O$^{2+}$ ions, which rearrange due to Coulombic repulsion over 10s of fs. Importantly, structural changes in the low fluence regime have implications for the design of two-pulse X-ray experiments that aim to study unperturbed liquid samples. Our simulations account for two key observations in the experimental data: the decrease in ambient water signal and an increase in low-angle X-ray scattering. They cannot, however, account for the experimentally observed 9 Å feature. A satisfactory account of this feature presents a new challenge for theory. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_10840 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Distinct transient structural rearrangement of ionized water revealed by XFEL X-ray pump X-ray probe experiment Stransky, Michal Lane, Thomas J. Gorel, Alexander Boutet, Sébastien Schlichting, Ilme Mancuso, Adrian P. Jurek, Zoltan Ziaja, Beata Plasma Physics Using X-ray free electron laser (XFEL) radiation to conduct an X-ray pump X-ray probe experiment, we studied strongly ionized water as part of our ongoing work on radiation damage. After irradiance with a pump pulse with a nominal fluence of ~$5 \times 10^5$ J/cm$^2$, we observed for pump-probe delays of 75 fs and longer an unexpected structural rearrangement, exhibiting a characteristic length scale of ~9 Å. Simulations suggest that the experiment probes a superposition of ionized water in two distinct regimes. In the first, fluences expected at the X-ray focus create nearly completely ionized water, which as a result becomes effectively transparent to the probe. In the second regime, out of focus pump radiation produces O$^{1+}$ and O$^{2+}$ ions, which rearrange due to Coulombic repulsion over 10s of fs. Importantly, structural changes in the low fluence regime have implications for the design of two-pulse X-ray experiments that aim to study unperturbed liquid samples. Our simulations account for two key observations in the experimental data: the decrease in ambient water signal and an increase in low-angle X-ray scattering. They cannot, however, account for the experimentally observed 9 Å feature. A satisfactory account of this feature presents a new challenge for theory. |
| title | Distinct transient structural rearrangement of ionized water revealed by XFEL X-ray pump X-ray probe experiment |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2402.10840 |