Collision-induced dissociation of Fen+ (n=2–19) with Xe: Bond energies, geometric structures, and dissociation pathways

The kinetic energy dependence of the collision-induced dissociation (CID) of Fe+n (n=11–19) with Xe is studied by using a guided ion beam mass spectrometer. As previously reported for smaller iron cluster ions, these iron cluster ions dissociate exclusively by evaporation, the sequential loss of Fe atoms. Bond energies for the larger iron cluster ions D0(Fe+n−1–Fe), n=11–19, as well as updated values for the smaller cluster ions, n=2–10, are reported. These energies are derived after explicit consideration of the effect of secondary collisions between Fe+n and Xe, and of the lifetimes of the energized iron cluster ions. Bond energies for neutral iron clusters are derived by combining these ionic bond energies with literature ionization energies for Fen. Except for the dimers, we find that the bond energies of ionic and neutral iron clusters are very similar and change nonmonotonically as a function of cluster size, with local maxima at n=6, 7, 13, 15, and 19; and local minima at n=8, 14, and 18. Evidence for the existence of weakly bound isomers of iron cluster ions is also observed.