Methyl Isocyanide (CH$_3$NC) and Acetonitrile (CH$_3$CN) are two complex organic molecules (COMs) which are detected in the interstellar medium and in comets (Remijan et al.2005). They are nodes of the very entangled chemical network leading to the molecular complexity. We aim at exploring the solid-state chemistry which may lead to COMs.
We developed a new experimental set-up named VENUS, in which we can deposit different reactants together on the cold surface (10K-40K). CH$_3$NC/CH$_3$CN and H/D atoms were co-deposited at different temperatures in presence or absence of water. Thanks to Infrared spectroscopy and mass spectrometry, we detected products and remnants after completing the depositions.
We obtained the following observations and measurements :
i) Methyl Isocyanide reacts with H, but Acetonitrile is unreacted.
ii) The total reactivities are decreased with the increase of the surface temperature.
iii) Hydrogenations, isomerization, and fragmentations are competitive mechanisms.
iv) Isotopic effects are observed.
v) The presence of water enhances the hydrogenation.
We will present the experimental results and discuss the chemical network in details, unveiling the presence of activation barriers and (very likely) the role of the quantum tunneling in the formation of COMs on grains.
Remijan, A. J., Hollis, J. M., Lovas, F. J., Plusquellic, D. F., & Jewell, P. R. 2005. The Astrophysical Journal (632)