CONSIDERATION OF THE CHEMISTRY OF RADON PROGENY

Although the early-time chemistry and physics of radon progeny are far from being completely understood, sufficient quantitative knowledge is now available from laboratory experiments to interpret certain observations and predict their behavior and fate. Here, attention is given to the two progeny, lead and bismuth. A significant fraction of the progeny are expected to exist in the singly charged state. Any initial association with an O2 molecule from the air will be rapidly replaced by polar molecules and thereby become rapidly hydrated with between five and eight molecules of water, depending on temperature and humidity. Substitution of a water molecule by an ammonia, alcohol, or perhaps other organic molecule is possible. Collisions of these cluster ion complexes with aerosol particles offer mechanisms of charge exchange, and incorporation with the particles. Failing interaction with preexisting aerosols, the clusters will remain in the singly charged state during growth and transport. The ultimate fate is then expected to be charge neutralization via recombination with cluster anions in the air, most probably NO3-(H2O)n.