INFRARED PHOTO-DISSOCIATION OF POLYATOMIC IONS

Dissociation of CF3I+, CF3Br+, and CF3Cl+ ions resulting from the absorption of a single 10 μ IR photon by highly vibrationally excited parent ions under collision-free conditions is reported. In each case, the only observed products are CF3+ + X. Dissociation yields as a function of photon wavelength for CF3I+ and CF3Br+ peak sharply at ∼950 cm-1 corresponding to a strong absorption frequency in the molecular ion. Product ion translational energy distributions are measured for CF3I+ and CF3Br+ photodissociation, and indicate that the energy release is ≪h v. The observed dissociation can be interpreted as resulting from the unimolecular decomposition of ions, initially formed with a total energy within 900-1000 cm-1 of the disociation limit, that absorb a single infrared photon. Thus, this process corresponds directly to the final step in IR multiphoton dissociation of polyatomic ions. © 1980 American Institute of Physics.