Auger electron emission from target ions under heavy-ion impact after molecular dissociation

The line shape of the (1s2s2p)4P (metastable) to (1s2)1S+e- Auger electron transition from heavy-ion impact is measured for targets containing carbon, nitrogen, oxygen and neon. The angular distribution of this transition is also measured for molecular gas targets containing carbon. Ar, Kr, Xe and U projectiles from the UNILAC were used with energy 1.4 MeV amu-1. It is found that the line shape depends strongly on the initial molecular target. Kinematic effects such as projectile-induced target recoil do not account well for these changes. A simple model is proposed that assumes the creation of a highly ionised molecule. The line shape is due to Doppler broadening from the velocity acquired by the dissociation of the molecule. Reasonable agreement between this Coulomb explosion model and the experimental results is found, allowing dissociation velocities to be calculated from the experimental line shapes.