Formation of radon decay product aerosols

Alpha decay carries away positive charge and electrons are stripped from the parent atom by its recoil. Therefore, the decay products are formed as positive ions. Air is ionised by radiation from the naturally occurring radionuclides in the air and on the ground and by cosmic rays. Production of one ion pair requires 32.5 eV if ionisation is caused by fast electrons, 35.6 eV if by alpha particles. The total energy dissipated in air per decay of Rn depends on the equilibrium ratio of the radon decay products. 

In the free atmosphere, the rate of production of small ions is in balance with the rate of neutralisation by recombination and the rate of attachment to condensation nuclei. Condensation nuclei, otherwise called Aitken nuclei, are submicrometre particles mainly pro- 

Most of the newly formed decay product clusters are positively charged and have a high mobility. The mobility is characterised by the diffusion coefficient that chiefly controls the formation of the radioactive aerosols by attachment and the deposition on surfaces. The measured values for the diffusion coefficient, D, range from 0.03 to 0.085 cm s depending on 

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