Scaling dynamics of aerosol coagulation

A combination of static and quasielastic light scattering and the theory of scaling solutions to Smoluchowski's equation was used to determine the absolute coagulation rate K0{'} and kernel homogeneity {λ} of a coagulating liquid-drop aerosol. Droplet sizes ranged from 0.23 to 0.42 {μ}m, implying Knudsen numbers in the range 0.26 and 0.14. The temporal evolution of the number concentration M0 and the modal radius rM of an assumed zeroth-order log-normal distribution showed near-power-law behavior similar to that predicted by the scaling theory. From the temporal scaling behavior of M0(t) and rM(t), the absolute coagulation rate was calculated. The coagulation rates from each method were in good agreement. The rate also agreed well with theory that corrected the Brownian rate, good for the continuum regime, by the average Cunningham correction factor. In addition, the time dependence of the moments M0 and rM, hence the determination of K0{'}, was in good agreement with a real-time numerical solution of Smoluchowski's equation for initial conditions analogous to our experimental ones.