Analysis of collision induced dissociation of Na-2(+) molecular ions

A full analysis of the collision induced dissociation of a diatomic molecular ion is presented for the first time. The experiment is essentially based on the simultaneous measurement of the momenta of the two fragments. This technique applied to the collision of Na2+ with a helium target reveals, at keV collision energies, the competition between two dissociation mechanisms: an impulsive mechanism when the target hits one Na+ core in a close encounter and an electronic mechanism when dissociation occurs after excitation of repulsive or weakly bound states.