ATOMIC CARBON IN THE UPPER ATMOSPHERE OF TITAN

The atomic carbon emission C-I line feature at 1657 angstrom (P-3(J)0-P-3(J)) in the upper atmosphere of Titan is first identified from the airglow spectra obtained by the Cassini Ultra-violet Imaging Spectrograph. A one-dimensional photochemical model of Titan is used to study the photochemistry of atomic carbon on Titan. Reaction between CH and atomic hydrogen is the major source of atomic carbon, and reactions with hydrocarbons (C2H2 and C2H4) are the most important loss processes. Resonance scattering of sunlight by atomic carbon is the dominant emission mechanism. The emission intensity calculations based on model results show good agreement with the observations.