Guided ion beam studies of the state-specific reactions of Fe+ (6D,4F) with CH3X (X = Cl, Br, I)

Reactions of Fe+ with CH3X (X = Cl, Br, I) are studied by guided ion beam techniques. State-specific reaction cross sections for production of FeCH3+ and FeX+ are presented for the 6D ground and the 4F first excited states of Fe+. The overall behavior seen in these reactions is similar to that seen in the analogous reactions of Co+ and Ni+, discussed in the preceding paper in this issue. The two states of Fe+ exhibit large differences in reactivity, with the 4F state generally being more reactive than the 6D state for production of FeX+ and FeCH3+. The only exception is for the exothermic formation of FeCH3+ below 0.7 eV in the CH3I system. We postulate that this is due to a potential energy surface crossing that is avoided at low kinetic energies due to spin-orbit interactions and is permitted at higher energies. Analysis of the threshold behavior of the endothermic reactions provides two determinations of D degree (Fe+-CH3) = 2.49 ± 0.13 and 2.47 ± 0.07 eV, in good agreement with previous values. Lower limits are placed on the bond energies for Fe+-X