Antimony and bismuth oxide cluster ions

Abstract

The formation of charged antimony and bismuth oxide clusters in a pulsed arc cluster ion source (PACIS) has been studied with time-of-flight mass spectrometric techniques. We compare series of antimony and bismuth oxide cluster anions with their known cationic counterparts. The anionic series (M₂O₃)_nMO₂⁻ and (M₂O₃)_nO₂⁻ have been predicted proceeding from the known cationic series (M₂O₃)_nMO⁺ and (M₂O₃)_nO⁺ by adding O²⁻ and have been experimentally established. All these series contain the metal atoms (M = Sb or Bi) in the formal oxidation state + 3. However, only in the case of antimony, oxygen rich oxide clusters appear, that can be explained with a gradual transition in the oxidation number from + 3 to + 5 of single antimony atoms in the cluster. To estimate the influence of the special oxide formation conditions comparative investigations with the PACIS and a laser vaporisation cluster source have been carried out for bismuth oxide cations. The similar oxide cluster distributions at comparable oxygen availability display clearly that the special thermodynamical stability of the discussed magic clusters is the significant driving force for their formation.