Zusammenfassung :

Am(III) L3 edge XAFS from Am(III) doped calcite crystals and ²⁴³Am treated ferrihydrite samples are investigated. The FT spectrum for the calcite exhibits a single low-R peak at R-D near 1.8 Å, which can be modeled as an oxygen shell (5-6 O at 2.40 Å). No shell splitting, which might be associated with the different TRLFS species is observed. Furthermore, there is no Am-Am interaction, excluding the presence of Am mineral clusters. The Am-O distance differs slightly from the Ca-O distance (2.36 Å) in calcite but in good agreement with structural parameters obtained in EXAFS studies on rare-earth element doped calcite. Comparing the difference in energy positions (DE) of the major XANES features for the Am(III) treated ferrihydrite samples reveals that the Am-O shell following heat treatment (i.e., transformation to a secondary species) shortens.