Analysis of EXAFS data from mixed-shell systems

A new method for analysis of EXAFS data from coordination shells containing two types of atoms distributed at two well defined distances is proposed. The method, which in effect isolates the individual contributions of the two subshells, can be viewed as a refinement of conventional techniques such as beat analysis and multi-shell least-squares fitting. No external information on the structure of any of the contributing subshells is required beyond the usual assumption of small or 'Gaussian' disorder. As much as fivefold reduction in the confidence limits of the coordination numbers in comparison with unrestricted multi-shell fits is demonstrated. The range of applicability and limitations of the method are discussed in detail.