Accurate labeling of the light-actinide O4,5 edges

In this short article, the accurate labeling of the O4,5 edges of the light actinides is addressed. The O4 and O5 edges are both contained in what is termed the ‘giant resonance’ and the smaller ‘pre-peak’ that is observed is a consequence of first-order perturbation by the 5d spin–orbit interaction on the 5d,5f exchange splitting. Thus, the small pre-peak in the actinide 5d→5f transition should not be labeled the O5 peak, but rather the ΔS=1 peak.