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Abstract: Metastable fractions for the dissociation of fullerene cations have been measured in a three-sector-field mass spectrometer. They have been determined with the same experimental setup as the kinetic energy release data published recently. A statistical model which includes cooling by radiation as required by the timescale of the experiment is used to deduce dissociation energies from the metastable fractions. The results are compared with values extracted from our kinetic energy release data and other experiments. [Copyright &y& Elsevier]

The recent addition of (i) a third sector field to our two sector field mass spectrometer (resulting in a BE1E2 field configuration) and of (ii) a high performance electron gun enables us now to study in detail the time dependence of the kinetic energy release distribution (KERD) over a relatively wide range of cluster ion lifetimes. Using this newly constructed device we have studied here for the first time KERDs and deduced binding energies BEs (using finite heat bath theory) of large rare gas cluster ions (an upper size limit in earlier studies arose from the fact that different naturally occurring isotopes will contribute to a chosen metastable peak when the size exceeds a certain value) and in addition of fullerene ions smaller and larger than C60+ (here again contaminating coincidences did not allow such studies earlier). Moreover, high precision KERD measurements for the decay of rare gas dimer ions in conjunction with model calculations (using recently calculated potential energy curves for the rare gas dimer ions) also enable us to obtain information on the dynamics and the mechanisms of the underlying spontaneous decay reactions Rg2+∗ → Rg+ + Rg. In addition, we are also reporting here a novel method (unified breakdown graph method) to determine cluster ion binding energies using a recently constructed tandem mass spectrometer BESTOF allowing us to measure fragmentation patterns arising from the unimolecular decay of molecular cluster ions induced by surface collisions. The fragmentation and reaction patterns of protonated ethanol cluster ions investigated here clearly demonstrate in contrast to some of the earlier cluster ion studies that unimolecular dissociation kinetics determines the formation of product ions in the surface-induced decomposition. [ABSTRACT FROM AUTHOR]

Abstract: Metastable ions C3HnN+ (n =1, 2 or 3) and C2H2 + produced by electron impact on the neutral C3H3N (acrylonitrile) undergo metastable decay reactions resulting in the fragment ions C3HmN+ (m =1, 2) or C2H2 +. We have monitored these reactions in a double focusing mass spectrometer of reversed B-E geometry. To identify the fragment ions and determine their kinetic energy release distribution (KERD), the mass-analyzed ion kinetic energy (MIKE) scan technique was utilized. For the above mentioned ions we obtained average KER values ranging from 9 up to 23meV. Moreover, the fractions of decaying ions were measured. We have found the existence of two states of the metastable C2H2 + ion, one with a short life time of about 0.27μs and the other one which is most likely a completely stable ion state. [Copyright &y& Elsevier]