Photoelectron spectroscopy and density-functional calculations of silver cluster anions doped with a cobalt atom: Size dependent sp–d interaction

Electronic structures of AgnCo− (n = 6–8) were investigated by photoelectron spectroscopy and density-functional calculations. The local spin magnetic moments on Co were found to be 2.04, 1.48, and 0 μB for n = 6, 7, and 8, respectively. A strong sp–d interaction in n = 8 allows the Co 3d orbitals to form a closed electronic shell, whereas the Co 3d shells in n = 6 and 7 remain open with finite spins under a weak sp–d interaction. The present result demonstrates significant size dependence of an sp–d interaction in a metal cluster containing a magnetic impurity.