New benzene absorption cross sections in the VUV, relevance for Titan's upper atmosphere

Fernando J. Capalbo, Yves Bénilan, Nicolas Fray, Martin Schwell, Norbert Champion, Et touhami Es-sebbar, Tommi T. Koskinen, Ivan Lehocki, Roger V. Yelle

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Benzene is an important molecule in Titan's atmosphere because it is a potential link between the gas phase and the organic solid phase. We measured photoabsorption in the ultraviolet by benzene gas at temperatures covering the range from room temperature to 215. K. We derived benzene absorption cross sections and analyzed them in terms of the transitions observed. No significant variation with measurement temperature was observed. We discuss the implications of our measurements for the derivation of benzene abundance profiles in Titan's thermosphere, by the Cassini/Ultraviolet Imaging Spectrograph (UVIS). The use of absorption cross sections at low temperature is recommended to avoid small systematic uncertainties in the profiles. We used our measurements, together with absorption cross sections from other molecules, to analyze four stellar occultations by Titan, measured by UVIS during flybys T21, T41, T41_II, and T53. We derived and compared benzene abundance profiles in Titan's thermosphere between approximately 530 and 1000. km, for different dates and geographical locations. The comparisons of our benzene profiles with each other, and with profiles from models of the upper atmosphere, point to a complex behavior that is not explained by current photochemical models.

Original languageEnglish (US)
Pages (from-to)95-109
Number of pages15
JournalIcarus
Volume265
DOIs
StatePublished - Feb 1 2016

Keywords

  • Atmospheres, composition
  • Occultations
  • Spectroscopy
  • Titan, atmosphere
  • Ultraviolet observations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Capalbo, F. J., Bénilan, Y., Fray, N., Schwell, M., Champion, N., Es-sebbar, E. T., Koskinen, T. T., Lehocki, I., & Yelle, R. V. (2016). New benzene absorption cross sections in the VUV, relevance for Titan's upper atmosphere. Icarus, 265, 95-109. https://doi.org/10.1016/j.icarus.2015.10.006