Electron stimulated desorption of O- and O-2(-) from condensed ozone: Possible implications for the heterogeneous photochemistry of stratospheric O-3

We have studied the desorption of negative ions following low energy electr on impact (0-15 eV) to ozone condensed in multilayer amounts on a cryogenic ally cooled gold surface. Intense desorption of O- is observed at low elect ron energies (below 4 eV) via pronounced resonances with an estimated desor ption cross section of the order of 10(-18) cm(2) (peak value). The resonan t features in the ion yield indicate that O- desorption is driven by dissoc iative electron attachment to O-3 molecules at or near the surface. While d issociative electron attachment (DA) from gas phase ozone generates the fra gment ions O- and O-2(-) at comparable intensities, desorption of O-2(-) fr om condensed ozone is strongly suppressed, being only weakly observed withi n a resonance located at 7 eV. Possible implications for the heterogeneous chemistry of ozone on polar stratospheric cloud (PSC) particles, namely pho to-induced dissociative electron transfer from the substrate, are discussed in the light of the effective O- desorption observed at low electron energ ies.