Ab Initio Confirmation of a Harpoon-Type Electron Transfer in a Helium Droplet

An ab initio study of a long-range electron transfer or "harpoon"-type process from Cs and Cs₂ to C₆₀ in a superfluid helium droplet is presented. The heliophobic Cs or Cs₂ species are initially located at the droplet surface, while the heliophilic C₆₀ molecule is fully immersed in the droplet. First, probabilities for the electron transfer in the gas phase are calculated for reactants with velocities below the critical Landau velocity of 57 m/s to account for the superfluid helium environment. Next, reaction pathways are derived that also include the repulsive contribution from the extrusion of helium upon the approach of the two reactants. Our results are in perfect agreement with recent experimental measurements of electron ionization mass spectroscopy [ Renzler, M.; et al., J. Chem. Phys. 2016, 145, 181101 ], showing a high possibility for the formation of a Cs₂-C₆₀ complex inside of the droplet through a direct harpoon-type electron transfer involving the rotation of the molecule but a negligibly low reactivity for atomic Cs.