RESUMO
Electron scattering on NO-2, NO-2 x (H2O), and NO-2 x (H2O)(2) was performed in two storage rings. We confirm the presence of earlier reported NO2-2 dianion resonances and show that they remain when water is attached. Importantly, hydration tunes the energy: each water molecule lowers the ground state energy by 0.8 +/- 0.3 eV relative to the monoanion. NO2-2 is observed to decay by two-electron emission, possibly in combination with fragmentation. NO(2-)2 x (H2O) mainly decays into NO-2 + H2O + e(-).
RESUMO
The cross sections for electron scattering on OH-(H2O)n for n = 0-4 were measured from threshold to approximately 50 eV. All detachment cross sections were found to follow the classical prediction given earlier [Phys. Rev. Lett. 74, 892 (1995)] with a threshold energy for electron-impact detachment that increased upon sequential hydration, yielding values in the range from 4.5 eV +/- 0.2 eV for OH- to 12.10 eV +/- 0.5 eV for OH-(H2O)4. For n > or = 1, we found that approximately 80% of the total reaction events lead to electron detachment plus total dissociation of the clusters into the constituent molecules of OH and H2O. Finally, we observed resonances in the cross sections for OH-(H2O)3 and for OH-(H2O)4. The resonances were located at approximately 15 eV and were ascribed to the formation of dianions in excited states.