Multifragmentation of molecules and clusters

Abstract

The multiple ionization and fragmentation of small polyatomic molecules and clusters,e.g. H2O, CH4, and C60 by fast H+, He+, and Oq+ ions were studied utilizing a position- and time-sensitive multiparticle detector which allows the coincident measurement of the momenta of correlated fragments. Thereby, akinematically complete image of the molecular break-up can be derived for each individual event. Of special interest are the “Coulomb explosion” processes, like H2 O→ H++ H++Oq+, where the measured dissociation energies and angular correlations show significant deviations from the pure Coulomb explosion model. For larger molecules and clusters, new phenomena may be expected. For example, using a classical molecular dynamics simulation, we have studied the break-up of hot Arn (n ≥ 100) clusters. For initial temperatures around 500 K various analytical tools consistently indicate critical behaviour in the expansion phase.