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

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

Molecular collisions, photoionization and dynamics: honouring Professor Vincent McKoy

“…Elastic and inelastic scattering of lowenergy electrons from gas-phase C 60 : elastic scattering angular distributions and coexisting solid-state features have been revisited by Tanaka et al [12] while Cl − kinetic-energy release distributions from chlorobenzene and related molecules in electron transfer experiments were presented by Kumar et al [13]. A combined experimental and theoretical study of helium adsorption on cationic hexaphenylbenzene (HPB), a propeller-shaped molecule, was investigated [14], and molecular synthesis in ices triggered by dissociative electron attachment to carbon monoxide was presented by Schmidt et al [15]. García-Abenza and co-workers [16] reported on a complete data set for the simulation of electron transport through gaseous tetrahydrofuran in the energy range 1-100 eV as a significant attempt to understand radiation damage in biological related molecules particle track simulations, whilst Randi et al [17] described elastic, electronically inelastic, total ionization and total cross sections for the scattering of electrons by trans-formic acid.…”