36th DPS Meeting, 8-12 November 2004
Session 20 Titan
Poster I, Tuesday, November 9, 2004, 4:00-7:00pm, Exhibition Hall 1A

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[20.13] Molecular nitrogen photoabsorption cross sections and line widths in the vacuum ultraviolet: applications to planetary atmospheric transmission models

G. Stark (Wellesley College), P.L. Smith, K. Yoshino (Harvard-Smithsonian Center for Astrophysics)

The analyses of VUV occultation measurements of the N2-rich atmospheres of Titan and Triton are hampered by the lack of fundamental spectroscopic data for N2. There is a need for reliable photoabsorption f-values and line widths for the approximately 100 electronic bands of N2 in the 80 to 100 nm wavelength region. We report measurements of these fundamental parameters of the absorption spectrum of 14N2 in the 94 100 nm spectral region. The room temperature absorption measurements were performed with the 6.65-meter vuv spectrometer at the Photon Factory synchrotron facility with a resolving power of approximately 125,000. A line-shape fitting routine is used to extract individual rotational line f-values and predissociation-broadened line widths within the fifteen bands reported in this study. Within individual bands, we find significant departures from the predicted line strength distributions based on isolated band models. Line width analyses within each band indicate that predissociation-broadening is often highly dependent on the rotational quantum number. We illustrate the importance of N2 line widths in the analysis of occultation measurements via N2 transmission models over selected wavelength regions.

We gratefully acknowledge funding support from NASA grant NAG5-9059.


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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.