Direct Evidence for the Sequential Decay C60z+→C58z+→C56z+→

Using a two sector field mass spectrometer in combination with a crossed beams ion source we have obtained direct experimental evidence that C60 fragment ions such as C58,C56,C54,...produced by electron impact ionization of C60 may be formed by unimolecular decay of the C60 parent ion involving sequential loss of C2. Moreover, by comparing experimental and theoretical breakdown graphs the overriding conclusion is that in the case of C56z+ production (with z=1,2,3) sequential loss of two C2 units dominates over the loss of a single C4 unit. copyright 1996 The American Physical Society