Volume 530, June 2011
|Number of page(s)||8|
|Section||Interstellar and circumstellar matter|
|Published online||18 May 2011|
Kinetics of the OCN− and HOCN formation from the HNCO + H2O thermal reaction in interstellar ice analogs
Université de Provence, laboratoire de Physique des Interactions Ioniques et Moléculaires, Centre de St-Jérôme, Avenue Escadrille Normandie-Niémen, 13397 Marseille France
2 Academia Sinica Institute of Astronomy and Astrophysics Astronomy-Mathematics Building, NTU, Taipei, ROC
Received: 3 November 2010
Accepted: 21 February 2011
Aims. We study in the laboratory the kinetics of the low-temperature OCN− and HOCN formation from the purely thermal reaction of solid HNCO and H2O. The cyanate ion OCN− is an intermediate in the isomerization process of isocyanic acid HNCO into cyanic acid HOCN in water ice.
Methods. We study the reaction, isomerization and desorption kinetics of the HNCO/OCN−/HOCN system using Fourier transform infrared spectroscopy.
Results. Activation energies of 26 ± 2 kJ mol-1 (3127 K) and 36 ± 1 kJ mol-1 (4330 K) are found for the HNCO + H2O → OCN− + H3O+ and OCN− + H3O+ → HOCN + H2O reactions respectively. Desorption energies of 37 ± 3 kJ mol-1 (4450 K) and 40 ± 3 kJ mol-1 (4811 K) are measured for HNCO and OCN−, respectively.
Conclusions. The present experiment has the important implication that the H2O + HNCO reaction alone cannot account for the observed abundances of solid OCN− in astronomical IR sources.
Key words: astrochemistry / ISM: molecules / molecular processes / molecular data
© ESO, 2011
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