Bicarbonate complexes of trivalent actinides - Stable or unstable?

The formation of the first Cm(III) bicarbonate complex is investigated by t ime resolved laser fluorescence spectroscopy (TRLFS) at an elevated CO2 par tial pressure of 11 bar in 1 m NaCl at room temperature. A high pressure ce ll was constructed for conducting spectroscopic studies at elevated pressur es using fiber optics. The experiments, performed under conditions (pH = 4. 4) where the formation of other complexes e.g. carbonate complexes can be n eglected, prove the presence of the previously postulated CmHCO32+ complex. The stability constant is confirmed to be log beta(CmHCO32+) = 1.9 -1 0.2 in 1 m NaCl.