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High Resolution UV Spectroscopy of H2 and N2 Applied to Observations of the Planets by SpacecraftThe next generation of high resolution UV imaging spacecraft are being prepared for studying the airglow and aurora of the Earth, the other terrestrial planets and the Jovian planets. To keep pace with these technological improvements we have developed a laboratory program to provide electron impact collision cross sections of the major molecular planetary gases (H2, N2, CO2, O2, and CO). Spectra under optically thin conditions have been measured with a high resolution (lambda/delta(lambda) = 50000) UV spectrometer in tandem with electron impact collision chamber. High resolution spectra of the Lyman and Wemer band systems of H2 have been obtained and modeled. Synthetic spectral intensities based on the J-dependent transition probabilities that include ro-vibronic perturbations are in very good agreement with experimental intensities. The kinetic energy distribution of H(2p,3p) atoms resulting from electron impact dissociation of H2 has been measured. The distribution is based on the first measurement of the H Lyman-alpha (H L(alpha)) and H Lyman-beta (H L(beta)) emission line Doppler profiles. Electron impact dissociation of H2 is believed to be one of the major mechanisms leading to the observed wide profile of H L-alpha from Jupiter aurora by the Hubble Space Telescope (HST). Analysis of the deconvolved line profile of H L-alpha reveals the existence of a narrow line peak (40 mA FWHM) and a broad pedestal base (240 mA FWHM). The band strengths of the electron excited N2 (C(sup 3) Pi(sub(upsilon) - B(sup 3)Pi(sub g)) second positive system have been measured in the middle ultraviolet. We report a quantitative measurement of the predissociation fraction 0.15 +/- 01(sup .045, sub .01) at 300 K in the N2 c'(sub )4 (1)sigma(sup +, sub g) - x(1)sigma(sup +, sub g)(00) band, with an experimental determination of rotational line strengths to be used to understand N2 EUV emission from Titan, Triton and the Earth.
Document ID
19980228109
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
Authors
Ajello, J.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Shemansky, D.
(University of Southern California Los Angeles, CA United States)
Kanik, I.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
James, G.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Liu, X.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Ahmed, S.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Ciocca, M.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Date Acquired
August 18, 2013
Publication Date
January 1, 1996
Publication Information
Publication: Journal of Electron Spectroscopy and Related Phenomena
Publisher: Elsevier Science B.V.
Volume: 79
ISSN: 0368-2048
Subject Category
Astronomy
Distribution Limits
Public
Copyright
Other

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