Fractal properties of propane soot by in-situ and ex-situ diagnostics for different agglomeration regimes

Sizing of the primary particles is obtained at different HABs by collecting (ex-situ method) the soot that impacts on a quartz probe as effect of thermophoresis. A diagnostic based on measurements of polarized light scattered by agglomerates has been proposed recently (di Stasio, 1999) to obtain, without sampling, the average size of the constituting primary particles, assumed in the Rayleigh regime. Fundamental advantages of light scattering techniques are, essentially, high spatial resolution (fractions of gin3), very scarce perturbation on particles under test by the probing light, possibility to perform optical measurements on suspended particles even in the case of very poor absorption. This is the case, for instance, of sulfate aerosols in atmosphere.