Polyynes and Cyanopolyynes: Their Synthesis with the Carbon Arc Gives the Same Abundances Occurring in Carbon-Rich Stars |
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Authors: | Franco Cataldo |
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Institution: | (1) Soc. Lupi Chemical Research Institute, Via Casilina 1626/A, 00133 Rome, Italy |
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Abstract: | Carbon vapour generated from a carbon arc or by laser ablation of graphite is reactive with simple molecules and atoms producing
end-capped polyyne chains. With these techniques both hydrogen-terminated polyynes as well as monocyano- and dicyanopolyynes
have been produced. Experiments based on arcing graphite electrodes can reproduce the molecular distribution of polyynes existing
around carbon-rich AGB stars. In fact, it has been found that the relative abundances of the polyynes produced in carbon arc
in vacuum decreases by a factor between 3 and 5 as the chain length increases by a C2 unit. An analogous trend has been observed both for polyynes and cyanopolyynes in the circumstellar environment around carbon-rich
stars. This fact suggests that the mechanism of formation of the polyynes in the carbon arc may be similar to that occurring
in the surroundings of the carbon-rich stars. Polyynes and cyanopolyynes represent authentic prebiotic molecules which appear
quite ubiquitous in the cosmos and should have played a role in the early organic chemistry preceding the appearance of life.
Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005. |
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Keywords: | polyynes cyanopolyynes dicyanopolyynes carbon vapor arc carbon-rich stars AGB stars relative abundance |
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