Criteria for automatic x-ray absorption fine structure background removal

Abstract

Criteria for terminating smoothing to remove a cubic spline background from the x-ray absorption coefficient are stated in terms of three parameters obtained from the k3 weighted Fourier transform of the resulting x-ray absorption fine structure data. The three parameters are HR, the average value of the transform magnitude between 0 and 0.25 Å, HM, the maximum value in the transform magnitude between 1 and 5 Å, and HN, the average value of the transform magnitude between 9 and 10 Å. The termination criteria are HR−HN ⩾0.05HM; or if HN ≳0.1HM, then HR ⩾0.1HM. The incorporation of the criteria into a computer program to facilitate automatic background removal is discussed. Examples of application of the technique to copper, β-PtO2, and ferritin samples are presented.