Kinetic energy distributions of product ions from singly and multiply ionized C2H2 molecules induced by 0.8Â MeV C+ collisions

We measure kinetic energy distributions (KEDs) of product ions from singly and multiply ionized acetylene, C2H2r+∗ (r = 1-4), generated as intermediate states prior to fragmentation in collisions between C2H2 and 0.8 MeV C+ ions, in single-electron capture conditions. The KEDs are systematically obtained as functions of the charge state r by performing coincidence measurements between momentum imaging of the product ions and counting of the number of emitted electrons. The KEDs of the fragment ions exhibit a variety of dependences on r, reflecting the variation of fragmentation dynamics and dominant fragmentation pathways. In particular, the KEDs of C2+ present a characteristic dependence on r because of the different symmetries of charge distributions in three-body fragmentation.