Decay pathway determination of even-size dicationic silver clusters: Ag-16(2+) and Ag-18(2+) revisited by pre-precursor selection and sequential decay

It is demonstrated how by selection of pre-percursor cluster ions Ag-2n+1(2 +) and collision-induced dissociation an ensemble of Ag-2n(2+) can be produ ced, which is not contaminated be Ag-n(+) clusters of the same size-to-char ge state ratio, n/z. By use of this technique, Ag-16(2+) and Ag-18(2+) prec ursor ensembles have been prepared for further investigations. They are obs erved to decay by neutral monomer evaporation, Ag-2n(2+) --> Ag-2n-1(2+) Ag, and trimer fission, Ag-2n(2+) --> Ag-2n-3(+) + Ag-3(+), and show no sig n of symmetric fission. (C) 2000 Elsevier Science B.V. All rights reserved.