Probing covalency with oxidant K edge x-ray absorption spectroscopy of UF4 and UO2

There are some interesting discrepancies between what has been observed experimentally and the predictions of cluster theory. In particular, the F 1s x-ray absorption spectroscopy (XAS) of uranium tetrafluoride and the U 4d XAS branching ratio for oxidized uranium are two cases in point. These discrepancies may be driven by the overestimation of covalency in cluster calculations