[ITAL]Infrared Space Observatory's[/ITAL] Discovery of C[TINF]4[/TINF]H[TINF]2[/TINF], C[TINF]6[/TINF]H[TINF]2[/TINF], and Benzene in CRL 618

Abstract

We report on the detection with the Infrared Space Observatory (ISO), for the first time in the circumstellar medium, of the polyacetylenic chains C 4 H 2 and C 6 H 2 and of benzene (C 6 H 6 ) in the direction of the proto-planetary nebula CRL 618. Surprisingly, the abundances of di-and triacetylene are only a factor of 2-4 lower than that of C 2 H 2 . Benzene is Ӎ40 times less abundant than acetylene. We suggest that the chemistry in CRL 618 has been strongly modified by the UV photons coming from the hot central star and by the shocks associated with its high-velocity winds. All the infrared bands arise from a region with kinetic temperatures between 200 and 250 K, probably the photodissociation region associated with the dense torus that surrounds the central star. C 4 H 2 and C 6 H 2 have also been detected in CRL 2688, so it seems that C-rich proto-planetary nebulae are the best organic chemistry factories in space.

Rotationally resolved infrared spectroscopy of adamantane

“…Adamantane may also be searched for in C-rich circumstellar envelopes, such as IRC+10216 or CRL618 where many small hydrocarbon molecules have already been identified. 46,47 Our work reports accurate transitions for 7 of the 11 IR active modes of adamantane but the three most intense bands are the CH stretching modes which could not be resolved in our work. To circumvent this problem, an experiment making use of the Jet-AILES apparatus is planned to record the jet-cooled absorption spectrum in the 3 μm region (see Cirtog et al 48 for a description of the Jet-AILES apparatus), which might be more appropriate for a potential detection in space using for example the high spectral resolution instruments available at the Very Large Telescope (see, e.g., CRIRES (Ref.…”

Heavy ion formation in Titan's ionosphere: Magnetospheric introduction of free oxygen and a source of Titan's aerosols?

“…Vuitton et al (2007) and later Vuitton et al (2009b) showed significant abundances of polyynes (C2H2, C4H 2, C6H 2, C, H 2) in Titan's atmosphere at 1100 km using a photochemical model constrained by INMS ion measurements. In Vuitton et al (2007) they also note that the abundance for the higher carbon chain polyynes within Titan's atmosphere did not decrease as fast as that in other photochemical models (Yung et al, 1984;Toublanc et al, 1995;Wilson and Atreya, 2004), the ISM (MacLeod et al, 1984;Remijan et al, 2006;Cernicharo et al, 2001) and/or laboratory measurements (Coll et al, 1999) as the number of carbon atoms increased in the carbon chain. It is also well known, as discussed in Thaddeus (1994Thaddeus ( , 1994Thaddeus ( , 1995 and Vuitton et al (2007), that unsaturated polyynes can polymerize into long carbon linear chains from which fullerenes can form (Hunter, 1994;Thaddeus, 1994Thaddeus, , 1995.…”

ISO Spectroscopy of Gas and Dust: From Molecular Clouds to Protoplanetary Disks

“…Several other new molecules have been detected in the envelopes around latetype stars and protoplanetary nebulae. Although not formally part of this review, the exciting SWS discoveries of C 6 H 6 (benzene), C 6 H 2 , C 4 H 2 (Cernicharo et al 2001a), and C 2 H 4 (Cernicharo et al 2001b) toward CRL 618 should be mentioned.…”