Crossed influence coefficients for accurate X‐ray fluorescence analysis of multicomponent systems

A thorough theoretical study of the typical iron–nickel–chromium ternary system confirms the essential variability of influence coefficients with composition, thus accounting for the limited validity of empirical coefficient procedures. The origin and mechanisms of coefficient variation are accurately described, namely by distinguishing between binary or ‘longitudinal’ variation, it being related to either an enhancement effect or the use of polychromatic excitation or possibly both, and ‘transverse’ variations resulting from fluorescence crossed effects as well as tertiary fluorescence if represented. As a consequence a general mathematical expression, including all these effects and exactly matching the theoretical intensity equations, is assigned to the coefficients for the entire range of compositions. On a practical basis, precision considerations allow to simplify these relationships considerably and reduce them to a fairly simple, flexible system of ‘crossed’ influence coefficients. Since it closely conforms to the fundamental principles of fluorescent emission, this new scheme should prove effective for determining multicomponent systems, namely by allowing accurate analysis to be performed over a wide range of compositions ‘without standards’.