Distortions of X-ray Absorption Spectra Measured with Fluorescence Yield

The 2p X-ray absorption spectra of 3d transition metal compounds measured with fluorescence yield (FY) appear distorted. It is shown thatthis distortion is intrinsic to FY detection and not due to self-absorption. It results from the final-state dependent variation of the fluorescence decay, which is more than 400%. The Auger decay is also final state dependent but the variation is only 25%. In the approximation that the final states do not interfere with each other (which is shown to be approximately correct for Ni2+). the FY spectral shape identifies with the X-ray absorption spectrum multiplied with its symmetry-dependent fluorecence decay. Results are given for the nickel 2p edge of Cs[NiCr(CN)6]·2H2O measured synchronously with FY and electron yield.