Size-Dependent Effects of Electron Solvation on the Kinetics of Ammonia Revealed on the Molecular Scale

The high relevance of electron solvation in several branches of physics, chemistry, and environmental science arises from its efficient electron transfer mechanism. The effect of solvated electrons on solvent structure has been considered local and transient due to a lack of real-space studies. An experiment was designed to study the impact of solvated electrons on the ammonia structure while adsorbed to Cu(110) using low-temperature scanning tunneling microscopy with an adjoined femtosecond laser. The enhanced molecular kinetics induced by the solvated electrons are explained using density functional theory and first-principles molecular dynamics. The electrons have a substantially different impact on the kinetics of ammonia within clusters below and above a cluster size threshold, reflecting hydrogen bond rearrangement (mass transport) and hydrogen bond cleavage (desorption), respectively. This size-dependent effect has implications on the efficiency of processes that involve solvated electrons. Altering the solvent structure more than transiently demands the subsequent solvation of two electrons.