Experimental investigation of nitrile formation from VUV photochemistry of interstellar ices analogs: acetonitrile and amino acetonitrile

¹ Université de Provence, Laboratoire de Physique des Interactions Ioniques et Moléculaires Centre de St-Jérôme, Avenue Escadrille Normandie-Niemen, 13397 Marseille, France
e-mail: gregoire.danger@univ-provence.fr
² Univ. Paris-Sud, Astrochimie et Origines, Institut dAstrophysique Spatiale, UMR 8617, Orsay, 91405, France
³ CNRS, Orsay, 91405, France

Received: 10 September 2010
Accepted: 4 October 2010

Abstract

Context. The study of the chemical reactivity in interstellar ices in astrophysical environments is an important tool for understanding the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. The laboratory simulations of the reactivity in ice analogs provide important information for understanding the reactivity in these environments. Here, we used these experimental simulations to trace some formation pathways of two nitriles, acetonitrile and amino acetonitrile, which are two potential precursors of amino acids in astrophysical environments.

Aims. The purpose of this work is to present the first experimental approach for the formation of acetonitrile and amino acetonitrile in interstellar-like conditions.

Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy and mass spectrometry to study the formation at 20 K of acetonitrile CH₃CN from VUV irradiation of ethylamine and of amino acetonitrile NH₂CH₂CN from VUV irradiation of ammonia: acetonitrile mixture. Isotopic substitutions are used to confirm identifications.

Results. We demonstrate that acetonitrile can be formed at 20 K from the VUV irradiation of ethylamine with a yield of 4%. Furthermore, in presence of ammonia, at 20 K and under VUV irradiation, the acetonitrile can lead to the amino acetonitrile formation. These results suggest that acetonitrile and amino acetonitrile can be formed in astrophysical environments that are submitted to VUV irradiations.