Unimolecular dissociation of singly- and multiply-charged fullerene ions

Abstract

The formation of fragment ions from C60 due to electron impact ionization leading to a bimodal fragmentation pattern with a minimum around the cluster size of 30 is investigated with help of mass spectrometric techniques. Based on a detailed analysis of the energetics and kinetics of the singly- and multiply-charged fragment ions by two-sector field mass spectrometry (MIKE-scans) we can conclude that on the one hand some of the dissociation reactions proceed via evaporation of an intact C6 + or C4 + unit (and not via the sequential loss of smaller molecular carbon units). On the other hand, measured appearance energies and the direct observation of sequential C2-loss reactions confirm that the sequential loss of neutral C2 units is the dominant production mechanism for Cn z+ fragment ions with sizes 40 < n < 60.