s-dhybridization and evolution of the electronic and magnetic properties in small Co and Ni clusters

Photoelectron spectra of cold Niₙ^- and Coₙ^- clusters revealed discrete electronic features for $n<10$ for Ni and 20 for Co. These features, mainly due to detachment of $4s$ electrons, merge with $3d$-derived features at larger cluster sizes, indicating the onset of significant s-d hybridization. The current results clearly revealed how the electronic structure of Ni and Co clusters evolves from molecular to bulklike in the early stage of cluster growth. They also provide insight into the origin of the enhanced magnetism in small Ni and Co clusters, due to the localized nature of the $3d$ electrons.