HCI-induced molecule fragmentation: non-Coulombic explosion and three-body effects

The study of highly charged ion-induced diatomic (CO) and triatomic (CO2) molecules fragmentation by the coincident measurement of the fragment momenta is presented. It is shown that the experimental results together with ab initio calculations including a large number of potential energy curves evidence the limitation of the Coulomb explosion model to reproduce the dynamics of the fragmentation. The geometry modification of the CO2 molecule during the breakup is explored and the concerted or sequential nature of the dissociation is discussed for two fragmentation channels. Finally, the fragmentation of the H2 molecules following collisions with slow multicharged ions is analysed for various projectiles and energies. From the energy spectra, the effect of the projectile on the H+ fragments is evidenced. This three-body effect is discussed in connection with the results of two model calculations including or not the role of the projectile. (orig.)