Kivimäki A, Wasowicz TJ, Richter R. Soft X-ray Induced Production of Neutral Fragments in High-Rydberg States at the O 1s Ionization Threshold of the Water Molecule.
J Phys Chem A 2021;
125:713-720. [PMID:
33434028 PMCID:
PMC7880560 DOI:
10.1021/acs.jpca.0c06940]
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Abstract
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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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