SHATTERING OF CLUSTERS UPON SURFACE IMPACT - AN EXPERIMENTAL AND THEORETICAL-STUDY

The shattering transition expected upon ultrafast heating has been obs erved in size selected (NH3)(n-1)NH4+ clusters, n = 4 to 40, upon impa ct at supersonic velocities on a graphite surface. As a function of th e impact velocity, the transition is between the recoil of the intact parent cluster and the appearance of small, n = 1,2,... charged fragme nts. As the cluster size increases, the transition becomes a sharper f unction of the impact velocity. The experimental fragmentation pattern is well accounted for by a distribution of maximum entropy subject to conservation of energy, atoms, and charge.