Low energy electron interaction with free and bound $SF5CF3:$ Negative ion formation from single molecules, clusters and nanofilms

The interaction of free electrons with the potent greenhouse molecule $SF5CF3$ is studied under different degrees of aggregation: single molecules at collision free conditions, clusters within a supersonic molecular beam and condensed molecules. Electron collisions with single molecules are dominated by $SF5−$ formation produced via dissociative electron attachment (DEA) within a resonance located below 2 eV. In clusters, undissociated parent anions $SF5CF3−$ (and larger complexes containing undissociated anions) are observed in addition to the fragment ions. This indicates that (i) $SF5CF3$ possesses a positive adiabatic electron affinity and (b) low energy attachment is partly channeled into nondissociative processes when the molecule is coupled to an environment. Electron impact to condensed phase $SF5CF3$ exhibits a remarkably strong $F−$ desorption signal appearing from a pronounced resonance located at 11 eV while in the gas phase at 11 eV only a weak DEA signal is observed. Electron induced desorption from sub-monolayers of $SF5CF3$ on an amorphous $H2O$ ice surface is found to be more efficient compared to desorption of $SF5CF3$ from a Xe surface. The implications of these results for the heterogeneous photochemistry of $SF5CF3$ adsorbed on ice or dust particles in the Earth’s atmosphere are discussed.