Relationship between the area of L 2,3 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.