The rest of his work can be linked to the common thread of the consequences of filling the atomic underlayer 5f on the physicochemical properties of actinides.
This filling plays an essential role in the behaviour of the 15 actinides, especially when these electrons are delocalized, from protactinium (Pa) to americium (Am).
This results in a high richness of oxidation degrees of the first actinides (usually from 3 to 6) and in the manifestation of particular effects in the series (electronic states characterized by the quantum number J).
After the curium (Cm), it is necessary, to carry out experiments, to synthesize isotopes of berkelium (Bk), einstenium (Es) and Fm by nuclear reactions with particle accelerators,[7][8][9] and separate them from irradiated targets, which he did at Orsay.
[11] At the same time, he participated in the study of thermodynamic[12][13] and spectroscopic[14][15] properties of elements 5f (and 4f) in connection with electronic transfers between these elements and their environment: covalence in two-phase solvent extraction systems and crystal field effect on solids, in particular single crystals examined at 4 K. Finally, he continued his research on the fundamental problems of radionuclide migration in the environment[16] (speciation, concentration effect, retention on colloids) and selective separation of actinides/lanthanides from the elements constituting spent nuclear fuel.