Chemistry in Acetonitrile–Water Films Induced by Slow (<15 eV) Electrons: Application to the Earth and Space Chemistry

Abstract

Acetonitrile and water are molecules detected not only in space but also in planetary atmospheres. On the Earth, the nitrile compound is emitted from biomass burning and can be found up to the stratosphere. Trapped in water ice cores, they may be exposed to energetic particles, photons and secondary electrons, and contribute to the formation of complex organic molecules. Here, we show that methanol is the main product from the effective reaction of low-energy (<15 eV) electrons with acetonitrile–water films deposited on a substrate maintained at 85 K. In this process, each of the molecules is decomposed by the colliding electrons, producing respectively methyl and hydroxyl radicals, which further recombine to form methanol, as supported by density functional theory (DFT) calculations. In addition, we also report production of a small amount of glycolonitrile, a key precursor of adenine. This information contributes to a better comprehension and description of chemistry of icy grains.