Projectile fragment-ion fragment-ion coincidences (PFIFICO) following fast ion impact on SF_6

摘要

We investigated the fragmentation of SF_6~(n+) (n≥2) produced by impact of 2 MeV He~(2+) ions on neutral SF_6. single time-of-flight spectra of the resulting fragment ions were acquired with special interest in molecular dications, as well as coincident time-of-flight spectra of two ions arising from the same parent molecule, both flight time measurements being triggered by projectiles scattered in forward direction. Momentum correlations derived from the time-of-flight spectra allowed us to give a detailed description of the dynamics of the underlying fragmentation processes. Kinetic energy distributions of fragments and fragment pairs were calculated from the time-of-flight peaks by a novel method using a regularisation algorithm. In order to obtain a detailed picture of the fragmentation process, ab initio calculations of the vertical double-ionisation potentials in the valence region as well as the dissociation energies for all relevant fragmentation channels were performed. the combination of experimental and computational data allowed us to correlate initial electronic states of the doubly ionised parent molecule with the resulting fragmentation channels and to explain their relative abundances in the spectra.