Initial- and final-state effects on screening and branching ratio in 2p x-ray absorption of size-selected free 3d transition metal clusters.

A comprehensive study of size-dependent initial- and final-state effects in 2p x-ray absorption of free, homonuclear 3d transition metal clusters from titanium through nickel in a size range of 1-200 atoms is presented. From atom to bulk the 2p --> 3d excitation in 3d transition metals shifts to higher photon energy, which can be explained by increasing valence electron derealization in the initial state. A cluster-size-dependent decrease of the L2,3 branching ratio at a constant 2p spin-orbit splitting can be attributed to core-hole screening effects for all investigated 3d transition metal clusters. For small manganese cluster ions, highly localized 3d orbitals with ferromagnetic spin coupling and a filled 3d majority spin subband are suggested by the experimental 2/7 x-ray absorption spectra. [ABSTRACT FROM AUTHOR]