| Mass-analyzed kinetic energy spectroscopy (MIKES) has been used to study the unimolecular and collision-induced dissociation (CID) of doubly charged carbon disulphide (CS22+), diaminolakanes (NH 3+(CH2)nNH3+ ) and singly charged carbon disulphide (CS2+) and hexafluorobenzene (C6F6+). The MIKES spectra for the CID of CS2+ ions to CS+ and S+ ions in collision with Ar at 6 keV laboratory energy show four dynamically distinguishable reaction pathways. These processes have been classified as electron-capture induced dissociation (ECID) and collision-induced charge-separation dissociation (CICSD). Detailed analysis of kinetic energy lost by CS22+ ions in forming product ions shows that S fragments originating from ECID are produced from ground state dications while CS fragments originate predominantly from the first or second electronically excited state of CS22. Two energetically distinct CICSD processes which result in pairwise formation of CS and S have been characterized with recoil kinetic energies of 3.4eV and 4.1 eV. These experimental observations are supported by ab initio quantum calculations. Coupling Electrospray Ionization (ESI) with double-focusing mass spectrometry, the MIKES spectra and the Kinetic energy release distribution (KERD) of doubly charged diaminoalkanes shown the charge location influenced by Coulomb repulsion. The dissociation of CS 2+ ions proceeds via four energetically distinct pathways which are strongly dependent upon the kinetic energy of the ion and the nature of the collision gas. CID with argon neutrals is dominated at all energies by the lowest energy threshold reaction, endothermic by about 6eV, while the energetics of the process is different and strongly dependent on the ion kinetic energy when lighter collision gases (He, H2 and D2) are used for collisional activation. Dissociation of C6F 6+ via C-F bond cleavage in CID with helium and argon has been studied at 3 keV kinetic energies. The kinetic energy distributions of the fragment ion, C6F5+, from helium and argon are uniquely different in that helium has a highly endothermic channel while argon collisions result in a highly exothermic channel. The exothermic process corresponds to energy release of ∼10 eV into translational mode during the collision and the endothermic process corresponds to transfer of ∼17 eV energy from translational to internal modes. |
