Etude experimentale et theorique de l'evolution d'un aerosol de dimension inferieure a 0,02 μm

Formation and evolution of ultrafine particles produced by radiolysis and photolysis

“…The experimental system we use [Perrin et al, 1978] is illustrated schematically in Figure 1. It is composed of three parts: (1) an air circulation circuit which consists of a spherical vessel (800 1) preceded or not by two high-efficiency particulate air (HEPA) filters, (2) an aerosol production device for radiolytic experiments; an air flow circulates over a radioactive source of actinium-227 and the radioactive gas (Actinon) is then introduced into the vessel (as to photolytic experiments, a high-pressure mercury vapor lamp enables the continuous creation of particles after injecting SO2 in the reaction chamber [Boulaud et al, 1975]), and (3) measuring circuits include a 'honey comb structure' diffusion battery [Sinclair, 1975] coupled with a condensation nuclei counter.…”

“…Just before this instant, at t = 0, the size distribution of the present aerosol is unimodal, with a mean geometric diameter equal to 0.036/•m and a standard deviation equal to 1.56. It becomes bimodal We compared[Perrin et aL, 1978] these results to the one just after injecting SO,_: a lot of particles with diameters less found in numerically resolving the classical coagulation equation. There is a qualitative improvement of the agreement between the classical coagulation theory and our measurements, and such agreement becomes quantitative if there is an overevaluation of the coagulation coefficient, obtained by taking into consideration the kinetic theory, only by the introduction of intermolecular forces which may in the case of ultrafine aerosols substantially increase the coagulation coefficient.…”