Larger argon atomic clusters undergo a size-specific transition from rigid to fluid forms as the cluster temperature is varied. The observed nature of this phase change, detected by measurement of the spectral line shape of a benzene dopant molecule, favors the phase-coexistence model of the cluster melting transition.

No abstract

No abstract

Threshold photoionization experiments on beams of rare gas atomic clusters doped with a single metal atom ( A k N ; N = 1-200) reveal pronounced discontinuities in cluster abundances as a function of N. Abundanm at the photoionization thresholds for clusters containing up to 60 atoms and fragmentation probabilities measured on a 5 0 -p~ time scale provide compelling evidence that the neutral clusters, as well as the corresponding ions, pack in icosahedral shells.The optimal packing of a finite number of equivalent spheres follows a noncrystallographic motif characterized by concentric icosahedral shells.' Filled-shell structures consist of N* = 13, 5 5 , 147, 309, ... spheres and are called Mackay icosahedra.2

No abstract