Localization of 3dand 4dElectrons in Small Clusters: The “Roots” of Magnetism

The photoelectron spectra of mass-selected negatively charged ${\mathrm{Ni}}_n^{-}$ and ${\mathrm{Cu}}_n^{-}$ clusters show similarities, which indicate an almost total localization of the Ni $3d$ orbitals corresponding to a maximum magnetic moment of $1{\mu }_B$ per Ni atom. The similarity between ${\mathrm{Ni}}_n^{-}$ and ${\mathrm{Cu}}_n^{-}$ vanishes for $n>\mathrm{}7\mathrm{}$ corresponding to an increase in $3d$ delocalization. The data of ${\mathrm{Pd}}_n^{-}$ clusters suggest a Ni-like (“magnetic”) electronic structure for $n=3\mathrm{}$– $6$ and a Pt-like (“nonmagnetic”) one for $n>\mathrm{}15\mathrm{}$. There are indications that neutral P${\mathrm{d}}_7$ is a closed shell species (spin zero ground state).