Study of neutralization of 218 Po ions by small ion recombination in O2, Ar, and N2

Three mechanisms of neutralization of Po(+)--electron transfer, electron scavenging, and small ion recombination--have previously been suggested. Considerable work has been conducted on the first two mechanisms. However, little information about small ion recombination is available. In the present study, this mechanism was studied by examining the neutralization rates of different Rn concentrations in N2, Ar, and O2 with the aid of a continuous Rn progeny monitoring system. The results showed that the neutralization rates in the three gases are of the order 1-4 s-1 at high Rn concentrations (higher than 40,000 Bq m-3). A linear relationship between the neutralization rate and the square root of Rn concentration (from 40,000 Bq m-3 to 810,000 Bq m-3) was obtained. Neutralization rates were higher in the gas with lower ionization potential. Further, the existence of a neutralization rate plateau at high Rn concentrations was strongly suggested.