Electron-transfer and neutral-loss reactions in collisions of CF 32+ with argon

Abstract

We have recorded the relative intensities of the product ions formed following collisions of CF 3 2+ with Ar at collision energies between 1.8 and 4.4 eV in the centre of mass frame. These experiments show that electron-transfer and neutral-loss reactions dominate the ion yield. The neutral-loss reaction produces CF 2 2+ whilst the electron-transfer reactions produce CF + and CF 2 + together with Ar +. The variation of the neutral-loss ion yield with the collision energy provides a first estimate for the bond energy of the weak CF 2 2+–F bond as 58 kJ mol −1. Unrestricted Hartree Fock/second order Moller-Plesset ab initio calculations indicate that the ground state of CF 3 2+ adopts a C 2 v equilibrium geometry. Complete active space self-consistent field/multireference configuration interaction calculations of the electronic states of CF 3 + at the C 2 v geometry of the dication have also been performed. Using these calculated state energies, together with Landau-Zener theory, to try to rationalise the electron-transfer reactivity, it appears likely that at least two electronic states of CF 3 2+ are present in the dication beam. The ground state of CF 3 2+ is predicted to react via electron transfer to form predominantly CF 2 +. An excited state of CF 3 2+ lying approximately 5 eV above the ground state is hence required to explain the presence of CF + ions that we observe in the experiments.