Abstract
The X-ray absorption sum rules for the spin and orbital moments are generalized, through the introduction of a spin-asymmetry parameter, to account for the spin dependence of the dipole matrix elements. This generalization is important for the analysis of L2,3-edge X-ray magnetic circular dichroism of rare-earth elements, for which the original sum rules erroneously predict an antiparallel alignment of the 4f and 5d moments. The corrections to the sum rules are of the same order as the extracted moments for these systems. A procedure to apply the generalized sum rules is given, which makes use of theoretical calculations in addition to experimental data; the procedure is illustrated for Tb metal.