We report the detection of linear and cyclic isomers of C3H and C3H2 towards various starless cores and review the corresponding chemical pathways involving neutral (C3Hx with x=1,2) and ionic (C3Hx+ with x = 1,2,3) isomers.
We highlight the role of the branching ratio of electronic Dissociative Recombination (DR) reactions of C3H2+ and C3H3+ isomers showing that the statistical treatment of the relaxation of C3H* and C3H2* produced in these DR reactions may explain the relative c,l-C3H and c,l-C3H2 abundances.
We have also introduced in the model the third isomer of C3H2 (HCCCH). The observed cyclic-to-linear C3H2 ratio vary from 110 + or – 30 for molecular clouds with a total density around 1e4 molecules.cm-3 to 30 + or – 10 for molecular clouds with a total density around 4e5 molecules.cm-3, a trend well reproduced with our updated model. The higher ratio for low molecular cloud densities is mainly determined by the importance of the H + l-C3H2 -> H + c-C3H2 and H + t-C3H2 -> H + c-C3H2 isomerization reactions.
Jean-Christophe Loison, Marcelino Agundez, Valentine Wakelam, Evelyne Roueff, Pierre Gratier, Nuuria Marcelino, Dianailys Nunnez Reyes, Josee Cernicharo, Maryvonne Gerin
(Submitted on 25 Jul 2017)
Comments: Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:1707.07926 [astro-ph.GA] (or arXiv:1707.07926v1 [astro-ph.GA] for this version)
From: Valentine Wakelam
[v1] Tue, 25 Jul 2017 11:43:42 GMT (1736kb)
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