Diagnostics of Collisions between Electrons and Water Molecules in Near-ultraviolet and Visible Wavelengths
AffiliationUniv Arizona, Lunar & Planetary Lab
Small solar system bodies
Electron impact ionization
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PublisherIOP PUBLISHING LTD
CitationD. Bodewits et al 2019 ApJ 885 167
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
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AbstractWe studied the dissociation reactions of electron impact on water vapor for several fragment species at optical and near-ultraviolet wavelengths (200?850 nm). The resulting spectrum is dominated by the hydrogen Balmer series, by the OH (A (2)?(+);?;X (2)?) band, and by the emission of ionic H2O+(A (2)A(1);?;X B-2(1)) and OH+(A (3)?;?;X (3)?(?)) band systems. Emission cross sections and reaction channel thresholds were determined for energies between 5 and 100 eV. We find that the electron impact dissociation of H2O results in an emission spectrum of the OH (A (2)?(+);?;X (2)?) band that is distinctly different from the emission spectra from other excitation mechanisms seen in planetary astronomy. We attribute the change to a strongly non-thermal population of rotational states seen in planetary astronomy. This difference can be utilized for remote probing of the contribution of different physical reactions in astrophysical environments.
VersionFinal published version
SponsorsNASA through a grant from the Space Telescope Science InstituteSpace Telescope Science Institute [HST-GO-15625.001, NAS5-26555]; European Union's Horizon 2020 research and innovation programme ; Slovak Research and Development AgencySlovak Research and Development Agency [APVV-15-0580]; Slovak Grant Agency for ScienceVedecka grantova agentura MSVVaS SR a SAV (VEGA) [VEGA 1/0733/17]