Vibrational predissociation spectra of the , n = 3-10, 12 clusters: Even-odd alternation in the core ion

We report vibrational predissociation spectra of the , n = 3-10, 12 cluster ions in the 700-2400 cm-1 range. The odd numbered clusters are consistent with their identification as . The even numbered clusters are based on the core ion, where the first two O2 molecules add to in locations that individually break the symmetry of the core ion, but together restore this symmetry. Beyond , subsequent O2 attachment yields bands close to that of neutral O2, indicating that the special character of the cluster is retained.