Electronic and structural evolution of Co-n clusters (n=1-108) by photoelectron spectroscopy - art. no. 153402

Well-resolved photoelectron spectra are reported for Co-n(-) (n = 1 - 108) clusters. The data provide evidence for structural transitions and reveal i n detail the molecular to bulk electronic evolution in Co clusters. Cluster s with n<20 behave molecularlike with discrete transitions and dramatic siz e variations. Clusters with n<greater than or equal to>20 behave bulklike w ith broad spectral features and smooth-size evolution. But discrete and wel l-resolved spectral features are observed around n = 55, evident of a highl y symmetric Co-55 cluster. The molecularlike to bulklike transition is also shown in the electron affinities as a function of size, which obey the met allic-droplet model above Co-20 and extrapolate to the bulk workfunction.