Search for evidence of C4N2 on Titan with new spectroscopic data
Abstract
The Composite Infrared Spectrometer (CIRS) onboard Cassini has recorded spectra in the far and mid-infrared since 2004 with a spectral resolution of up to 0.5 cm-1. Mismatch between observed spectra and model spectra obtained from the available line lists has led us to study the spectroscopic parameters of HC3N, C4H2 and C2N2, the longest gas phase carbon chains observed so far on Titan. Band intensities, hot band intensities, and line lists were systematically verified by comparison with new laboratory spectra. Erroneous band intensities as well as an absence or shortage of hot band transitions in the line lists leading to model-data mismatches and inaccurate quantifications have been found.
Improvement in the spectroscopic parameters has led to the detection of 13C isotopologues of HC3N [1] and C4H2 [2]. The study on C2N2 opens the way to the detection of 15N isotopologues whose abundances could give some clues to understand the origin and the evolution of Titan's atmosphere [3]. Also, the higher accuracy of spectroscopic data used to model CIRS spectra will facilitate the search for longer carbon chains on Titan such as HC5N, C6H2 and C4N2. Our recent measurements obtained at the SOLEIL synchrotron far infrared beam line of band intensities of C4N2 in the far and mid infrared domain have shown strong discrepancies with previous results [4]. Following the intensity measurements, a careful analysis of high resolution data has led to the first line lists for C4N2, which gives us the chance to determine precise abundance upper limits of this molecule in Titan's atmosphere.- Publication:
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European Planetary Science Congress
- Pub Date:
- September 2013
- Bibcode:
- 2013EPSC....8..106J