The diffusion coefficient, D, of the radon-220 (thoron) daughter 212Pb (ThB) was measured at 82.4 and 101 kPa as a function of relative humidity (RH) using the diffusion tube method. For 35%< RH <85%, D was 0.036 and 0.029 cm2 s-1 for 82.4 and 101 kPa, respectively. The diameter of the ThB particles calculated from D was 1.354 and 1.365 nm for the respective pressures. For RH <35%, D decreased linearly with decreasing relative humidity and the calculated particle diameter was related to the relative humidity by the same equation. © 1988.
Su, Y. F., Newton, G. J., Cheng, Y. S., & Yeh, H. C. (1988). Experimental measurements of the diffusion coefficients and calculated sizes of Pb-212 particles. Journal of Aerosol Science, 19(6), 767–770. https://doi.org/10.1016/0021-8502(88)90011-0