Abstract

We have studied the desorption of negative ions following low energy electron impact (0–15 eV) to ozone condensed in multilayer amounts on a cryogenically cooled gold surface. Intense desorption of O− is observed at low electron energies (below 4 eV) ia pronounced resonances with an estimated desorption cross section of the order of 10−18 cm2 (peak value). The resonant features in the ion yield indicate that O− desorption is driven by dissociative electron attachment to O3 molecules at or near the surface. While dissociative electron attachment (DA) from gas phase ozone generates the fragment ions O− and O2− at comparable intensities, desorption of O2− from condensed ozone is strongly suppressed, being only weakly observed within a resonance located at 7 eV. Possible implications for the heterogeneous chemistry of ozone on polar stratospheric cloud (PSC) particles, namely photo-induced dissociative electron transfer from the substrate, are discussed in the light of the effective O− desorption observed at low electron energies.

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