Emission Cross Sections of the Lyman-Birge-Hopfield Band System in Molecular Nitrogen Induced by Electron Impact Excitation

HR: 0800h
AN: SA11A-0213 [Abstracts]
TI: Emission Cross Sections of the Lyman-Birge-Hopfield Band System in Molecular Nitrogen Induced by Electron Impact Excitation
AU: * Malone, C P
EM: Charles.Malone@jpl.nasa.gov
AF: Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Johnson, P V
EM: Paul.V.Johnson@jpl.nasa.gov
AF: Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Ajello, J M
EM: Joseph.M.Ajello@jpl.nasa.gov
AF: Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Kanik, I
EM: Isik.Kanik@jpl.nasa.gov
AF: Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: Emissions from the Lyman-Birge-Hopfield (LBH) band system in N₂ (a ¹Π_g → X ¹σ_g⁺) are the most prominent molecular features below 180 nm in the Earth's atmosphere [Kanik et al., Phys. Chem. Earth (C), 25, 573, 2000]. LBH emissions continue to be of interest as a sensitive test of N₂ density distributions and photoelectron flux in the dayglow and secondary electron flux in the aurora. Furthermore, recent measurements with the onboard Ultraviolet Imaging Spectrograph (UVIS) experiment by the Cassini spacecraft of the Saturnian system, in particular Titan, have invigorated the need for improved N₂ cross sections.
The present work utilized a large vacuum chamber, a detector platform that provided vertical and horizontal movement, a Faraday cup, and an electron gun providing an electron beam of fixed energy. The detector platform enabled the LBH emissions to be observed, using the UVIS engineering flight spare, at multiple radial positions relative to the electron beam axis, which was used to map the glow resulting from electron impact excitation of an optically thin swarm of N₂ gas. Normalization of the LBH emissions was provided by comparison with well known NI emissions. The absolute 100 eV LBH emission cross section was used to renormalize the LBH emission cross sections of [Ajello and Shemansky, JGR, 90, 9845, 1985].
Acknowledgement: This work was carried out at JPL, Caltech, under contract with NASA and at LASP, UC (Boulder). This research was performed while CPM held a NRC Research Associateship Award at JPL.
DE: 2400 IONOSPHERE (6929)
DE: 9800 GENERAL OR MISCELLANEOUS
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005