Laser diagnostics of nanometric soot particles from diesel engines

Summary form only given. Soot particles from combustion processes are one of the major component of urban aerosols. These particles are highly polymorphous. The smaller, almost spherical particles, (typically 20 to 60 nm in radius) undertake aggregation processes occurring during combustion and possibly during transport in the atmosphere: numerous particles with a fractal structure are produced. The impact on health of these particles, especially the smaller, is important since these particles deposited in lungs are highly toxic: carcinogenic molecules (like polycyclic aromatics) are adsorbed on the soot surface. Unfortunately, because of their size, monomers are rarely taken into account in aerosol analysis and especially in gravimetric studies. Therefore, the development of optical methods to deduce the size distribution and composition of urban aerosols (especially soot particles) over the whole size range is an important challenge. This needs to develop new experimental schemes and models to deduce the scattering properties of fractal soot particles. For that purpose, we have undertaken multiwavelength and multi-angle scattering experiments on a distribution of soot particles.