Slow electron attachment as a probe of cluster evaporation processes

TL;DR

This study investigates how slow electron attachment to alkali clusters induces evaporation, providing insights into cluster bonding, evaporation kinetics, and enabling analysis of cluster populations through experimental and theoretical methods.

Contribution

It offers a comprehensive analysis of electron attachment and evaporation processes in metal clusters, including a new relation between dissociation energies and methods to infer neutral cluster populations.

Findings

Revealed nontrivial restructuring of anion abundances after electron attachment

Developed a detailed model of evaporative cascades and cluster heating

Derived a new relation between dissociation energies of different charge states

Abstract

Neutral alkali clusters efficiently capture low-energy electrons with the aid of long-range polarization attraction. Upon attachment, the electron affinity and kinetic energy are dissipated into vibrations, heating the cluster and triggering evaporation of atoms and dimers. This process offers a novel means to explore nanocluster bonding and evaporation kinetics. The present work investigates the formation of ${Na}_N^-$. A crossed-beam experiment reveals that relative anion abundances become strongly and nontrivially restructured with respect to the neutral precursor beam. This restructuring is explained in quantitative detail by an analysis of evaporative cascades initiated by the attachment. The analysis thus furnishes a complete description of the electron attachment process, from initial attraction to final rearrangement of the cluster population. In addition, the paper describes a systematic derivation of cluster evaporation kinetics and internal temperature distributions; a new relation between the dissociation energies of cationic, neutral and anionic metal clusters; and a scenario for inferring the neutral cluster population in the supersonic beam from the cationic mass spectrum.