Localization of 3 d and 4 d Electrons in Small Clusters: The “Roots” of Magnetism

The photoelectron spectra of mass-selected negatively charged Niₙ^- and Cuₙ^- clusters show similarities, which indicate an almost total localization of the Ni $3d$ orbitals corresponding to a maximum magnetic moment of 1μB per Ni atom. The similarity between Niₙ^- and Cuₙ^- vanishes for $n>7$ corresponding to an increase in $3d$ delocalization. The data of Pdₙ^- clusters suggest a Ni-like (``magnetic'') electronic structure for n0ex0ex=0ex0ex3-- $6$ and a Pt-like (``nonmagnetic'') one for $n>15$. There are indications that neutral Pd₇ is a closed shell species (spin zero ground state).