IR Spectrum of C8H2: Integrated Band Intensities and Some Observational Implications
✍ Scribed by Fr. Shindo; Y. Bénilan; P. Chaquin; J.-C. Guillemin; A. Jolly; Fr. Raulin
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 113 KB
- Volume
- 210
- Category
- Article
- ISSN
- 0022-2852
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✦ Synopsis
Polyynes are of astrophysical interest since they appear to be involved in organic chemistry in very different mediums. In Titan's atmosphere, the lightest polyyne, C 4 H 2 , was detected by Voyager. Recently C 4 H 2 and C 6 H 2 have been discovered in a protoplanetary nebula, suggesting polyynes as a possible chemical pathway to PAH (polycyclic aromatic hydrocarbons). Moreover, several experimental simulations and modeling imply their production from the photochemistry of methane and their involvement in the formation of organic aerosols. After the study of C 4 H 2 and C 6 H 2 spectra in the UV and IR wavelength range, we report here the first spectrum of gaseous C 8 H 2 in the range 400-4000 cm -1 at room temperature and low resolution. The task was hardly achieved because of the high instability of this molecule with temperature and pressure. To avoid exothermic polymerization, the compound was mixed with a solvent. We have performed a separate spectroscopic study of the solvent to determine C 8 H 2 partial pressure within the mixture. This allowed us to calculate C 8 H 2 integrated band intensities. In the studied wavelength range, C 8 H 2 presents three main bands similar to those of C 6 H 2 in terms of vibrational type, position, and relative intensity. To study the possible identification of these polyynes by spatial observatories (Cassini-Huygens, ISO), we have also measured the C 6 H 2 and C 8 H 2 infrared spectra in the range 400-1500 cm -1 at 0.35 cm -1 resolution.