An analysis of the OI 1304 a dayglow using a Monte Carlo resonant scattering model with partial frequency redistribution

A Monte Carlo model of the atomic oxygen 1304 A airglow triplet has been developed which accurately describes the transport of resonance radiation under very optically thick conditions. Partial frequency redistribution, temperature gradients, pure absorption, and multilevel scattering are accounted for properly. Analysis of a recent rocket experiment which observed the 1304 A dayglow shows that all features of the data can be explained by photoelectron impact excitation and resonant scattering of sunlight. The latter source dominates below 100 and above 500 km, and is stronger at intermediate altitudes than previously thought. Recent observations of the photoelectron flux from AEE are consistent with both the 1304 and 1356 A dayglow, as are the laboratory cross-sections of Stone and Zipf (1974) for electron excitation of the OI 3S and 5S levels . There is no need to lower the laboratory cross-sections by a factor of 2 as has been suggested by previous work. The OI 1304 A emission can now be used with confidence to study excitation processes and atomic oxygen densities in planetary atmospheres.