Historical Development of EXAFS

Abstract

The Extended X-ray Absorption Fine Structure (EXAFS) has been known for over 50 years, but only recently has its power for structure determination been appreciated. The first experimental detection of fine structure past absorption edges were by Fricke (1920)¹ and Hertz (1920).² The first structure detected was the near edge structure (Coster 1924,³ Lindh 1921,⁴ 1925⁵) which could be explained by the theory of Kossel (1920).⁶ However, as the experimental measurements extended the detected fine structure to hundreds of eV past the edge (the EXAFS) (Ray 1929,⁷ Kievet and Lindsay 1930⁸) a new explanation was required. The temperature dependence in EXAFS was first experimentally noted by Hanawalt (1931).^9,10 Kronig (1931)¹¹ first attempted an explanation of the EXAFS in condensed matter using the newly developed Quantum Mechanics. His explanation utilized the energy gaps at the Brillouin zone boundaries and thus depended explicitly on the long range order in the solid. Following Azaroff (1963)¹² we will call this theory a long range order (LRO) theory and the other class of theories short range order (SRO). LRO theory is fundamentally in error, but it took over 40 years for the error to be discovered (Stern 1974).¹³