Energetics and dynamics of decaying cluster ions

The recent addition of (i) a third sector field to our twosector field mass spectrometer (resulting in a BE1E2 fieldconfiguration) and of (ii) a high performance electron gunenables us now to study in detail the time dependence of thekinetic energy release distribution (KERD) over a relativelywide range of cluster ion lifetimes. Using this newlyconstructed device we have studied here for the first time KERDsand deduced binding energies BEs (using finite heat bath theory)of large rare gas cluster ions (an upper size limit in earlierstudies arose from the fact that different naturally occurringisotopes will contribute to a chosen metastable peak when thesize exceeds a certain value) and in addition of fullerene ionssmaller and larger than (here again contaminatingcoincidences did not allow such studies earlier). Moreover, highprecision KERD measurements for the decay of rare gas dimer ionsin conjunction with model calculations (using recentlycalculated potential energy curves for the rare gas dimer ions)also enable us to obtain information on the dynamics and themechanisms of the underlying spontaneous decay reactions. In addition, we are also reportinghere a novel method (unified breakdown graph method) todetermine cluster ion binding energies using a recentlyconstructed tandem mass spectrometer BESTOF allowing us tomeasure fragmentation patterns arising from the unimoleculardecay of molecular cluster ions induced by surface collisions.The fragmentation and reaction patterns of protonated ethanolcluster ions investigated here clearly demonstrate in contrastto some of the earlier cluster ion studies that unimoleculardissociation kinetics determines the formation of product ionsin the surface-induced decomposition.