Collision-induced dissociation processes of Nb+4 and Fe+4: Fission vs evaporation

Abstract
Collision‐induced dissociation (CID) of Nb+4 and Fe+4 with Xe has been studied over an energy range of 0–20 eV with a new instrument designed to study cold cluster ions. The energy dependences of the cross sections are presented. It is found that the lowest energy pathway for Nb+4 CID is fragmentation into molecular ions, or fission. Analysis of this process yields D0(Nb+2–Nb2)=4.3±0.3 eV. Fe+4, on the other hand, fragments only by sequential loss of Fe. Analysis of the lowest energy process gives D0(Fe+3–Fe)=1.8±0.2 eV. No evidence for molecular Fen fragments is observed.