Cluster size distribution, factors affecting

A model has been developed to calculate the size distributions of the short lived decay products of radon in the indoor environment. In addition to the classical processes like attachment, plate out and ventilation, clustering of condensable species around the radioactive ions, and the neutralization of these ions by recombination and charge transfer are also taken into account. Some examples are presented showing that the latter processes may affect considerably the appearance and amount of the so called unattached fraction, as well as the equilibrium factor. 

The threshold volume fraction, c, depends not only on the spatial dimensionality but also on extrinsic factors. For a 3D, continuous, random mixture, d is ideally 15% values for other dimensions are listed in Table 7. However, c may be easily affected by the state of dispersion, size, shape, orientation, and distribution of the conductive phase. Therefore, it is best determined empirically. Finally, the prefactor o depends on details of ionic and molecular interactions and can only be computed from specific microscopic models. The important feature to be appreciated here is that the topological and geometrical information of the cluster connectivity is lumped together in the (c-c ) factor whereas the microscopic diffusion information and various interactions are contained in the prefactor o. ... 

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