Fragmentation of multiply ionized CF₃–CH₂F induced by charge-changing collisions with fast carbon ions

Abstract

We have investigated multiple ionization and fragmentation of 1, 1, 1, 2-tetrafluoroethane (CF₃–CH₂F) in charge-changing collisions with 580-keV C⁺. By measuring the number of emitted electrons in each collision, we obtained the charge state (r) distribution of multiply ionized CF₃–CH₂[r+*]F ions transiently formed as intermediate states prior to fragmentation. The mean charge states of CF₃–CH₂[r+*]F in single-electron (1e)-capture, 1e-loss, and double-electron-loss collisions were determined to be 1.9, 3.2, and 4.0, respectively. Time-of-flight mass spectra of the product ions from CF₃–CH₂[r+]F were obtained as a function of r from coincidence measurements with the number of emitted electrons. Production of specific fragment ions and variation of the fragmentation patterns were systematically revealed up to r = 4. For example, it was found that proton emission becomes the dominant decay process from multiply ionized CF₃–CH₂[r+]F. The results also show that coincidence measurements can distinguish ion species with the same mass-to-charge ratio but different charge states. The characteristic features of the fragmentation processes of CF₃–CH₂[r+*]F were investigated by the correlation among the product ions for r ≥ 2. C⁺ and C₂⁺ fragment ions are emitted to the same side as H⁺ even at r = 2, reflecting the structural feature of the asymmetric location of the heavier atoms (F) in the molecule.