Molecular synthesis in ices triggered by dissociative electron attachment to carbon monoxide

Abstract

Abstract Chemical reactions in mixed molecular ices as relevant in the context of astrochemistry can be initiated by electron-molecule interactions. Dissociative electron attachment (DEA) as initiating step is identified from the enhancement of product yields upon irradiation at particular electron energies. Herein, we show that DEA to CO leads to the formation of HCN in mixed CO/$$\hbox {NH}_{{3}}$$ NH 3 ice at electron energies around 11 eV and 16 eV. We propose that this reaction proceeds via insertion of the neutral C fragment into a N–H bond. In the case of CO/$$\hbox {H}_{{2}}$$ H 2 O and CO/$$\hbox {CH}_{{3}}$$ CH 3 OH ices, a resonant enhancement of the yields of HCOOH and $$\hbox {CH}_{{3}}$$ CH 3 OCHO, respectively, is observed around 10 eV. In both ices, both molecular constituents exhibit DEA processes in this energy range so that the energy-dependent product yield alone does not uniquely identify the relevant DEA channel. However, we demonstrate by comparing with earlier results on mixed ices where CO is replaced by $$\hbox {C}_{{2}}\hbox {H}_{{4}}$$ C 2 H 4 that DEA to CO is again responsible for the enhanced product formation. In this case, $$\hbox {O}^{\cdot -}$$ O · - activates $$\hbox {H}_{{2}}$$ H 2 O or $$\hbox {CH}_{{3}}$$ CH 3 OH which leads to the formation of larger products. We thus show that DEA to CO plays an important role in electron-induced syntheses in molecular ices. Graphical abstract