Electronic and geometric properties of exohedral sodium- and gold-fullerenes

The electronic and geometric properties of gas-phase exohedral C60NaN-, C70 NaN-, and C60AuN- cluster anions are investigated. Time-of-flight mass spec trometry and photoelectron spectroscopy (PES) reveal complex-specific arran gements of the sodium and the gold atoms on the fullerene cage. The electro n affinity of C60AuN clearly shows even-odd alternation with the number of Au atoms, which suggests a "dry" structure where Au atoms aggregate as a cl uster on the C-60. In contrast, C60NaN and C70NaN show a "wet" structure ha ving the Na atoms packed into stable trimers on the surface. For C60NaN (N = 0 to 4), PES experiments at a high photodetachment energy (5.81 eV) allow us to deduce the net charge transferred from the sodium atoms to the lowes t unoccupied molecular orbital of the fullerene. For larger C60NaN, moreove r, a metallic transition is shown to occur at N similar to 13, and analysis of the adiabatic electron affinity variations allows the identification of the first magic sizes corresponding to electronic shell closure in the sod ium layer. (C) 2001 American Institute of Physics.