Astro-electrochemistry of NH3 clusters and ice: e− trapping, stability, and electron transfer

Abstract

Quantifying electron trapping and transfer to small molecules is crucial for interfacial chemistry. In an astrochemical context, we study how NH3 clusters in both crystalline and amorphous forms can capture low-energy electrons to form ammoniated electrons. Electron affinities, vertical detachment energies, and vertical attachment energies were computed via ab initio static and dynamics simulations, (DFT, DLPNO-CCSD(T);AIMD), for (NH3)n clusters (n = 4, 5, 6, 8, 14, 23, and 38). Our results indicate that the clusters could trap and stabilize the unpaired electron which is always externally localized on the clusters. Interactions of the ammoniated electron clusters with astrochemically relevant molecules indicate that electron transfer to water and methanol are feasible, forming the radical anions (H2O)−· and (CH3OH)−·. The trapping of electrons by both crystalline and amorphous NH3 ices, and subsequent transfer to small molecules, highlights ‘astro-electrochemical’ reactions, and has implications for both astrochemistry as well as terrestrial cluster science.