When
3:30 p.m., Nov. 17, 2009
Where
Kuiper Space Sciences 308
Dr. Hiroshi Imanaka from the UA Department of Chemistry/SETI Institute is the scheduled speaker.
Abiotic formation of complex organic molecules is a necessary step towards the origin of life. In Titan’s N2-CH4 atmosphere, an evidence of formation of organic macromolecules was recently discovered by the Cassini-Huygens mission (Waite et al., 2007). Previous study of the vacuum UV photolysis of N2/CH4 gas mixtures indicates that photoionization of N2 by EUV radiation plays a major role in initiating the production of complex organic molecules such as benzene and toluene. This result is understood via a mechanism by which N2 catalytically acts to focus short wavelength EUV radiant energy with subsequent energy transfer to the carbon bearing substituents via dissociative charge transfer to methane. It is not clear, however, how much nitrogen is incorporated in Titan’s organic haze. Many aspects of the nitrogen fixation process by EUV-VUV photochemistry have not been fully understood.
We demonstrate the first evidence of nitrogenated organic haze production by EUV-VUV irradiation of a N2/CH4 gas mixture. The accumulated solid materials at 82.5 nm and 60 nm irradiations (10-25~10-24g/hv) are characterized with Laser Desorption Ionization- Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry (LDI-FTICR-MS). The obtained ultra-high-resolution mass spectra enable the unambiguous CHNO formula assignments, and they show the predominance of highly nitrogenated compounds in both solid materials. The statistical analyses of thousands of CHNO compounds reveals the state selected nitrogen incorporation of the ground state N(4S) and the excited state N(2D) into organic macromolecules, and implies the importance of N(2D) and HCCN radicals in the formation of nitrogenated organic aerosols in the Titan atmosphere.
Abiotic formation of complex organic molecules is a necessary step towards the origin of life. In Titan’s N2-CH4 atmosphere, an evidence of formation of organic macromolecules was recently discovered by the Cassini-Huygens mission (Waite et al., 2007). Previous study of the vacuum UV photolysis of N2/CH4 gas mixtures indicates that photoionization of N2 by EUV radiation plays a major role in initiating the production of complex organic molecules such as benzene and toluene. This result is understood via a mechanism by which N2 catalytically acts to focus short wavelength EUV radiant energy with subsequent energy transfer to the carbon bearing substituents via dissociative charge transfer to methane. It is not clear, however, how much nitrogen is incorporated in Titan’s organic haze. Many aspects of the nitrogen fixation process by EUV-VUV photochemistry have not been fully understood.
We demonstrate the first evidence of nitrogenated organic haze production by EUV-VUV irradiation of a N2/CH4 gas mixture. The accumulated solid materials at 82.5 nm and 60 nm irradiations (10-25~10-24g/hv) are characterized with Laser Desorption Ionization- Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry (LDI-FTICR-MS). The obtained ultra-high-resolution mass spectra enable the unambiguous CHNO formula assignments, and they show the predominance of highly nitrogenated compounds in both solid materials. The statistical analyses of thousands of CHNO compounds reveals the state selected nitrogen incorporation of the ground state N(4S) and the excited state N(2D) into organic macromolecules, and implies the importance of N(2D) and HCCN radicals in the formation of nitrogenated organic aerosols in the Titan atmosphere.
General
LPL Colloquium
Outreach
Undergraduate
Graduate