Soft X-ray induced production of neutral fragments in high-Rydberg states at the O 1s ionization threshold of the water molecule
Kivimäki, Antti; Wasowicz, Tomasz J.; Richter, Robert (2021-01-12)
Kivimäki, A., Wasowicz, T. J., & Richter, R. (2021). Soft X-ray Induced Production of Neutral Fragments in High-Rydberg States at the O 1s Ionization Threshold of the Water Molecule. The Journal of Physical Chemistry A, 125(3), 713–720. https://doi.org/10.1021/acs.jpca.0c06940
© 2021 American Chemical Society. This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe202103117068
Tiivistelmä
Abstract
Dissociation of water molecules after soft X-ray absorption can yield neutral fragments in high-Rydberg (HR) states. We have studied the production of such fragments by field ionization and ion time-of-flight (TOF) spectrometry. Neutral HR fragments are created at all resonances below the O 1s ionization potential (IP) and particularly within 1 eV above the O 1s IP. The latter effect is due to the recapture of the O 1s photoelectrons into HR orbitals of the molecular water ion after the emission of a fast Auger electron. H₂O+(HR) fragments subsequently dissociate, yielding neutral H(HR) and O(HR) fragments, as were found by measuring the TOF spectra by pulsed field ionization. Such measurements were carried out at the O 1s → 4a₁ and 2b₂ resonances as well as just above the O 1s IP. The TOF spectra also reveal two series of oscillatory structures that are attributed to quantum beats involving Lyman emission in one of the series and field ionization of H(HR) fragments in the other series.
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