Sc Kα, and Kβ X-ray fluorescence spectra

Abstract

Scandium Kα 1,2, Kα″, Kβ 1,3, Kβ″, and Kβ 5 X-ray fluorescence spectra were measured with a two-crystal X-ray fluorescence spectrometer for Sc(metal) and various scandium compounds. The following have been clarified. (i) The Kβ″ satellite was strong for ScF 3 but weak for Sc 2O 3. The chemical effects on the intensity and energy of the Kβ″ have been interpreted for ScF 3 and Sc 2O 3 by the electronic structure calculations of DV- Xα molecular-orbital method. The Kβ″ is assigned to the electron transition from an antibonding molecular orbital which is formed between Sc 3 p and ligand 2 s to the ls −1hole. (ii) The transition assignment of Kβ 5 i.e. the electric quadrupole transition from 3 d to 1 s, has been found false for Sc. The Kβ 5, has been assigned to the electric dipole transition from valence molecular orbitals to the 1 s −1 hole. (iii) The Kα″ satellite of ScF 3 was found to be significantly weaker than those of other Sc compounds, whereas the Kβ″ satellite of ScF 3 stronger than those of other compounds. These apparently contradictory experimental results have been consistently rationalized through a electron transfer mechanism which is supported by DV- Xα molecular-orbital calculations. The strong Kβ″ satellite signifies the formation of strong molecular orbitals through which the 3p −1 shake-off hole is delocalized, resulting in a weak multivacancy ( KM → LM) Kα″ satellite. (iv) The Kα″ and Kβ″ satellites for Sc metal was found to be strong, because the conduction electrons moves more freely to screen the core hole than the 3p −1 hole does. The Kβ″ satellite has been assigned to the hole transition from 1s −1 to an antibonding molecular orbital which is formed between the center Sc 3 p and the neighboring Sc 3 p orbitals. (v) While the Kα 1, chemical shift was found to be well correlated to the electronegativity of the neighboring atoms, the Kβ 1,3 shift has not been directly correlated to the effective charges on the Sc atom. The latter is due to a large orbital interaction between Sc 3 p and ligand atomic orbitals. It was concluded from the chemical shift of Kα 1 that the 3 d orbital population after the formation of chemical bond is decreased from that of the free Sc atom.