[en] Careful measurement of the diffusion coefficient of RaA shows that it is a function of the length: flowrate ratio of the diffusion tube used (or of age) and leads to the conclusion that there is no single diffusion coefficient for RaA, and to the hypothesis that the diffusivity depends upon the chemical nature of the reaction product formed between RaA and the gaseous environment. In agreement with this hypothesis, the electrostatic collection efficiency of RaA in atmospheres of various gases correlates with the ionization potential of the gases. There is a clear need to investigate further the chemistry of radon daughters in order to understand their dosimetry and deposition in the human lung. (author)