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Nitrogen Incorporation in CH4-N2 Photochemical Aerosol Produced by Far UV IrradiationNitrile incorporation into Titan aerosol accompanying hydrocarbon chemistry is thought to be driven by extreme UV wavelengths (lambda < 120 nm) or magnetospheric electrons in the outer reaches of the atmosphere. Far UV radiation (120 - 200 nm), which is transmitted down to the stratosphere of Titan, is expected to affect hydrocarbon chemistry only and not initiate the formation of nitrogenated species. We have examined the chemical properties of photochemical aerosol produced at far UV wavelengths using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), which allows for elemental analysis of particle-phase products. Our results show that aerosol formed from CH4/N2 photochemistry contains a surprising amount of nitrogen, up to 16% by mass, a result of photolysis in the far UV. The proportion of nitrogenated organics to hydrocarbon species is shown to be correlated with that of N2 in the irradiated gas. The aerosol mass greatly decreases when N2 is removed, indicating that N2 plays a major role in aerosol production. Because direct dissociation of N2 is highly improbable given the immeasurably low cross-section at the wavelengths studied, the chemical activation of N2 must occur via another pathway. Any chemical activation of N2 at wavelengths > 120 nm is presently unaccounted for in atmospheric photochemical models. We suggest that reaction with CH radicals produced from CH4 photolysis may provide a mechanism for incorporating N into the molecular structure of the aerosol. Further work is needed to understand the chemistry involved, as these processes may have significant implications for prebiotic chemistry on the early Earth and similar planets.
Document ID
20120009529
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Trainer, Melissa G. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Jimenez, Jose L. (Colorado Univ. Boulder, CO, United States)
Yung, Yuk L. (California Inst. of Tech. Pasadena, CA, United States)
Toon, Owen B. (Colorado Univ. Boulder, CO, United States)
Tolbert, Margaret A. (Colorado Univ. Boulder, CO, United States)
Date Acquired
August 25, 2013
Publication Date
April 1, 2012
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC.JA.6207.2012
Funding Number(s)
CONTRACT_GRANT: NSF ATM-0449815
CONTRACT_GRANT: NNX11AD82G
CONTRACT_GRANT: NOAA NA08OAR4310565
CONTRACT_GRANT: NNX08AG93G
CONTRACT_GRANT: NNX09AB72G
CONTRACT_GRANT: NNX07AV55G
Distribution Limits
Public
Copyright
Public Use Permitted.

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