Relationship between the area of L2,3 x-ray absorption edge resonances and the d orbital occupancy in compounds of platinum and iridium

Abstract

The relationship between the intensity of the L₂ and L₃ x‐ray absorption threshold resonances and d orbital occupancy has been investigated for a series of compounds of platinum and iridium and the pure metals, using Xα‐SW molecular orbital calculations to obtain the unoccupied d orbital states. The change in d orbital occupancy caused by formation of the core hole was found to be fairly constant in different compounds and the pure metal. The difference between the d orbital occupancy in platinum metal and the d orbital occupancy in a given platinum compound agrees well with the calculated effective charge on the platinum atom in the compound. The areas of the threshold resonance lines were obtained by a deconvolution of the absorption edge into a Lorentzian component and an underlying ’’step’’ representing the onset of absorption to continuum states. For a series of platinum compounds, a linear relationship was obtained between the unoccupied d orbital states calculated in the core hole potential, and the sum of the areas of the L₂ and L₃ threshold resonance lines (corrected for the different degeneracies of the initial state). However, this relationship could not be applied to IrO₂ because of the absence of transitions to empty d states at the top of the valence band.