Chloride complexation of rutherfordium. X-ray absorption fine structure spectroscopy of Zr and Hf in HCl

Chemical behavior of the first transactinide element, rutherfordium (Rf), in hydrochloric acid has been investigated by ion-exchange and solvent extraction methods together with the group-4 homologues Zr and Hf. Recently, relativistic molecular density-functional calculations of electronic structure were performed for hydrated, hydrolyzed, and chloride complexes of Rf, Zr, and Hf. The chloride complexation and hydrolysis of Rf have been discussed so far, but there are no detailed structural data of Zr and Hf in HCl that are essential to discuss the experimental results of Rf and to perform the theoretical calculations. The extended X-ray absorption fine structure (EXAFS) measurements can provide information on the local environment around the central atom such as the atomic number (Z) and the number of neighboring atoms (N) and their distance from the central atom (R). In the present work, we have measured EXAFS spectra of Zr and Hf complexes systematically in 1.0-11.9 M HCl. A change in the complex structure with the HCl concentration is discussed by referring to the anion-exchange behavior of Rf as well as Zr and Hf. (orig.)