Velocity map imaging of the photodissociation of CF3I+ in the (A)over-tilde←(X)over-tilde band

The photodissociation dynamics of CF3I+ has been investigated within the (A) over tilde <--(X) over tilde band by means of velocity map ion imaging. The CF3I+ cation is prepared by resonance-enhanced multiphoton ionization of CF3I via the [X E-2(3/2)]6p, [2]5(0)(1) band, and the ((X) over tilde E-2(3/2)) ground-state population in the CF3I+ ion is unambiguously characterized by using photoelectron spectroscopy. Photodissociation of the state-selected CF3I+ ion results in fragmentation to both CF3++I and CF3+I+. The translational energy distribution derived from the two-dimensional images of the CF3+ fragments shows vibrational progressions that provide detailed information on the channeling of the parent internal energy into the dissociation process. The translational fragment shows a one-to-one dependence on the excitation energy, which is typical of a single-photon dissociation process. The observation of a repeated pattern of rings in the CF3+ images with an interval of similar to800 cm-1 indicates that the nu(2) umbrella mode of the CF3+ fragment is excited upon dissociation. The low-kinetic-energy release observed in this channel indicates that substantial energy is deposited into the internal degrees of freedom of the CF3+ fragment and suggests that the dissociation is controlled by the Franck-Condon factors between the parent ion and fragments. The translational energy distribution of the I+ fragment is independent of the excitation wavelength and includes a feature peaking at near-zero kinetic energy. Plausible mechanisms for the CF3+ and I+ dissociation channels are discussed in terms of the observed kinetic energy and anisotropy distributions derived from the two-dimensional ion images. (C) 2003 American Institute of Physics.