Interdisciplinary round-robin test on molecular spectroscopy of the U(VI) acetate system

In the advent of the 2nd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2014), an inter-laboratory round-robin test (RRT) was initiated. The main goal of this RRT was the comprehensive molecular analysis of a simple aqueous com-plexing system – U(VI) acetate – which was selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods applied by leading laboratories in actinide or geochemical research. Ultimately, more than 40 scientists hosted at twenty insti-tutions in seven countries participated.
The outcome of this RRT can be considered on two levels: First, conformities as well as discrepancies in the results of each spectroscopic technique and their sources are evaluated. The raw data from the experimental approaches were found to be generally consistent. In particular, for complex setups such as accelerator-based X-ray absorption spectroscopy, the agreement between the raw data was surprisingly high. By contrast, the data obtained using luminescence spectroscopy turned out to be strongly related to the chosen acquisition pa-rameters. Second, the potentials and limitations of coupling various spectroscopic and, in particular, theoretical approaches for the comprehensive study of actinide molecule com-plexes are assessed. The additional benefits of the combined approach with regard to the exploration of the aqueous speciation of the U(VI) acetate system are elaborated.