Penning ionization electron spectroscopy of CO2 clusters in collision with metastable rare gas atoms

Electron attachment to CO2 embedded in superfluid He droplets

Electron attachment to CO₂ embedded in superfluid He droplets leads to ionic complexes of the form (CO₂)_n^– and (CO₂)_nO^– and, at much lower intensities, He containing ions of the form He_m(CO₂)_nO^–. At low energies (<5 eV), predominantly the non-decomposed complexes (CO₂)_n^– are formed via two resonance contributions, similar to electron attachment to pristine CO₂ clusters. The significantly different shapes and relative resonance positions, however, indicate particular quenching and mediation processes in CO₂@He. A series of further resonances in the energy range up to 67 eV can be assigned to electronic excitation of He and capture of the inelastically scattered electron generating (CO₂)_n^– and two additional processes where an intermediately formed He* leads to the nonstoichiometric anions (CO₂)_nO^–.