Dissociation pathways of sulfur dioxide clusters and mixed sulfur dioxide-water clusters

Abstract A reflectron-time-of-flight mass spectrometer (RTOFMS) coupled with a femtosecond multiphoton ionization technique is used to study the combined metastable and collision-induced dissociation of sulfur dioxide clusters and mixed sulfur dioxide-water clusters. From the dissociation patterns, the general structural arrangement of the clusters is clearly identified: (SO 2 ) m ·+ clusters have a SO 2 ·+ core solvated by SO 2 molecules; [SO(SO 2 ) n ] ·+ and [S(SO 2 ) n +1 ] ·+ have a structure of SO ·+ · (SO 2 ) n and (SO) 2 ·+ · (SO 2 ) n , respectively. For [HSO 2 (SO 2 )] + clusters, the ion core is HSO 2 + . H 3 SO 3 + appears to have two isomeric structures: one HSO 2 + · H 2 O, the other H 3 O + · SO 2 .