Fragmentation dynamics and geometrical arrangement of diatomic molecular clusters

Overview & Synopsis

The analysis of a kinematically complete ion-cluster collision experiment provides insight in the dynamics of the ionized cluster dissociation. The gas phase targets allow to study the cluster in a simple environment and to determine their intrinsic properties for further condensed states. Small van der Waals clusters of N2 and CO are produced in the supersonic expansion of a gas jet and irradiated by a low energy highly charged ion beam produced by the ARIBE/GANIL facility. Using our experimental set-up COLTRIMS (COLd Target Recoil Ion Momentum Spectroscopy) it is made possible to measure in coincidence the 3-D momentum vectors of the charged fragments resulting from the collision. We have performed experiment to investigate the fragmentation dynamics and geometry of N2 and CO dimers and trimers using a projectile beam Ar9+ with the 15 qkeV energy. Following multiple electron capture, the target undergoes two or three body dissociation. For three body channels, two distinct processes have been identified in which the van der Waals and covalent bond breaks either simultaneously or sequentially. Additionally, the Coulomb explosion imaging technique has been used to determine the three dimensional structure of the N2 and CO molecular dimers and trimers. We found that the N2 and CO molecules sit perpendicularly to the dimer axis in a planar (H) or non-planar (X) configuration and that (N2)3 and (CO)3 trimers exhibit an equilateral triangular geometry.