Photoelectron Spectroscopy of Metal Cluster Ion Beams

Metal clusters in the size range of a few to several hundreds of atoms are one of the most interesting frontiers of molecular physics and chemistry. One of the reasons for this interest is that they may serve usefully as molecular models of bulk surfaces . Somewhere within this 2–1000 size range it is expected that metallic behavior will set in: the sparse set of well-defined single quantum levels of the atom becoming a more complicated set of molecular orbitals in the 2 and 3 atom clusters, and then evolving (slowly?) toward the band structure of the bulk metallic phase. Somewhere along the way, the catalytic properties of these clusters will begin to resemble that of surfaces of the bulk metal. Detailed study of the physical and chemical nature of these small objects may therefore play a key role in the development of a fundamental and predictive understanding of metallic surfaces and heterogeneous catalysis.