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Abstract: We have measured the kinetic energy release distributions for unimolecular C2 loss from singly and multiply charged endohedral La@C80 z+ and La@C80 z+ ions for charge states z =1–3. Using finite heat bath theory, we deduce the dissociation energies for loss of C2. The charge state z has no statistically significant effect on the dissociation energies. The dissociation energies of endohedral fullerene ions are larger than those of the corresponding empty fullerene ions by a few tenths of an electron volt, but the differences are barely statistically significant. The small differences also imply that the complexation energies of La@C n z+ and La@C n −2 z+ are identical within the experimental errors, for n =80 and 82 and all charge states. [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]

The high resolution double focusing mass spectrometer of reversed Nier-Johnson geometry was used in research of ionization and fragmentation processes of ethanol molecules C2H5OH. Using the mass-analyzed ion kinetic energy technique, fragmentation paths and kinetic energy release distributions were examined for the four fragmentation reactions: C2H6O+ → C2H5O+, C2H6O+→C2H3O+, CH3O+→CH2O+ and CH3O+ → CHO+. For all fragment ions from these reactions mean values of kinetic energy release ∊were determined. We calculated mean values of ∊as 22.70 meV, 62.15 meV, 30.25 meV, and 117.20 meV for C2H5O+, C2H3O+, CH2O+, and for CHO+ ions, respectively. [ABSTRACT FROM AUTHOR]

Abstract: We have measured kinetic-energy-release distributions (KERD) for spontaneous dissociation of electronically excited dimer ions of krypton and xenon, formed by electron impact ionization of neutral precursors. The data cannot be reconciled by decay of the strongly bound II(1/2u) state that successfully explains dissociation of and . Instead, the KERD is dominated by contributions from the weakly bound II(1/2g) state that has so far escaped a convincing experimental characterization. The present data can be utilized to assess the accuracy of ab initio potential energy curves of this state. [Copyright &y& Elsevier]

Abstract: Doubly charged ions produced by electron impact ionization of toluene undergo metastable decomposition. We have determined decay channels for and the average kinetic energy release (KER) by applying the MIKE scan technique. We observe several reactions that have not been reported previously, including H2 elimination from . The KER distribution for H2 loss shows no evidence for a reverse barrier. The average KER is <0.1 eV; it exhibits a distinct time dependence and isotope effect. On the other hand, some charge separation reactions reported previously in the literature are likely due to isotopic interference. [Copyright &y& Elsevier]