Dissociation limit and dissociation dynamic of CF4+: Application of threshold photoelectron-photoion coincidence velocity imaging

Dissociation of internal energy selected CF4+ ions in an excitation energy range of 15.40-19.60 eV has been investigated using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. Only CF3+ fragment ions are observed in coincident mass spectra, indicating all the (XT1)-T-2, A(2)T(2), and (BE)-E-2 ionic states of CF4+ are fully dissociative. Both kinetic energy released distribution (KERD) and angular distribution in dissociation of CF4+ ions have been derived from three-dimensional TPEPICO time-sliced images. A parallel distribution of CF3+ fragments along the polarization vector of photon is observed for dissociation of CF4+ ions in all the low-lying electronic states. With the aid of F-loss potential energy curves, dissociation mechanisms of CF4+ ions in these electronic states have been proposed. CF4+ ions in both (XT1)-T-2 and A(2)T(2) states directly dissociate to CF3+ and F fragments along the repulsive C-F coordinate, while a two-step dissociation mechanism is suggested for (BE)-E-2 state: CF4+((BE)-E-2) ion first converts to the lower A(2)T(2) state via internal conversion, then dissociates to CF3+ and F fragments along the steep A(2)T(2) potential energy surface. In addition, an adiabatic appearance potential of AP(0)(CF3+/CF4) has also been established to be 14.71 +/- 0.02 eV, which is very consistent with the recent calculated values. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792368]