Comparison of reactive nucleation of silver and alkali clusters in the presence of oxygen and water

The nucleation of silver-atom vapor in the presence of O-2 and H2O molecule s has been investigated by photoionization mass spectrometry and compared t o the case of alkali-atom vapor. Relative intensities in mass spectra show that silver vapor does not react with H2O molecules, in contrast with sodiu m vapor. When O-2 and H2O are simultaneously present, hydroxided products a re observed. Results emphasize the role of stable units, (NaOH)(2) or (KOH) (2), for alkalies, and more complex hydrated or hydroxided systems, involvi ng trimers, for silver. Similarities are found with water dissociative adso rption on an oxygen-predosed silver surface.