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UV photolysis of polyynes at λ=254 nm and at λ>222 nm

Published online by Cambridge University Press:  30 June 2008

Franco Cataldo ,
Giovanni Strazzulla  and
Susana Iglesias-Groth
Franco Cataldo
Affiliation:
Actinium Chemical Research, Via Casilina 1626/A, 00133 Rome, Italy INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
Giovanni Strazzulla
Affiliation:
INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
Susana Iglesias-Groth
Affiliation:
Instituto de Astrofisica de Canarias, Via Lactea s/n, E-38200, La Laguna, Canary Islands, Spain e-mail: franco.cataldo@fastwebnet.it
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Abstract

For the first time the kinetic rate constants of the UV photolysis of polyynes C6H2, C8H2, C10H2, C12H2 and C14H2 under rigorously inert atmosphere have been determined in three different solvents: n-hexane, n-heptane and decalin. First- or pseudofirst-order kinetics appear suitable to describe the photolysis of these molecules and k values in the range between 3.0×10−3 s−1 and 4.6×10−3 s−1 have been determined. The unique exception is represented by C6H2 which photolyses more slowly with k=3.2×10−4 s−1. Two different UV sources have been used in the present study: a low-pressure mercury lamp having a monochromatic emission at 253.7 nm and a medium-to high-pressure lamp with a continuous emission between 222 nm and 580 nm. The results are of interest in the understanding, and also the modelling, of the fate of polyynes released by carbon-rich stars in the interstellar medium or the polyynes released by comets in their active phase.

Keywords

astrochemistrydecompositionkineticsphotolysispolyynesUV radiation
Type
Research Article
Information
International Journal of Astrobiology , Volume 7 , Issue 2 , April 2008 , pp. 107 - 116
Copyright
Copyright © 2008 Cambridge University Press

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