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Intensities of the Martian N 2 electron‐impact excited dayglow emissions
Author(s) -
Fox Jane L.,
F. Hać Nicholas E.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50435
Subject(s) - martian , excited state , mars exploration program , atomic physics , airglow , ground state , physics , excitation , electron ionization , atmosphere of mars , atomic electron transition , ionization , astrobiology , spectral line , atmospheric sciences , astronomy , ion , quantum mechanics
The first N 2 emissions in the Martian dayglow were detected by the SPICAM UV spectrograph on board the Mars Express spacecraft. Intensities of the (0,5) and (0,6) Vegard‐Kaplan bands were found to be about one third of those predicted more than 35 years ago. The Vegard‐Kaplan band system arises from the transition from the lowest N 2 triplet state ( A 3Σ u + ; v ′ ) to the electronic ground state ( X 1Σ g + ; v ″ ). It is excited in the Martian dayglow by direct electron‐impact excitation of the ground N 2 ( X ) state to the A state and by excitation to higher triplet states that populate the A state by cascading. Using revised data, we compute here updated intensities of several of the bands in the N 2 triplet systems and those involving the a 1 Π g state, the upper state of the Lyman‐Birge‐Hopfield bands. We find that the predicted limb intensities for the (0,5) and (0,6) Vegard‐Kaplan bands are consistent with the measured values.