(528h) Effects of Condensate Layers on the Light Scattering and Absorption of Combustion Soot Aerosols

Soot particles are composed of nanometer carbonaceous particles that are aggregated together into micrometer fractal aggregates. These particles during combustion production can have adsorbed layers of poly aromatic hydrocarbons (PAH's) or in our atmosphere can have adsorbed layers of water and hydrocarbons. The present state of the art of light scattering provides for the multiple scattering of small particles typically below the Rayleigh limit (size less than the wavelength of light) in multiple scattering fractal aggregates. This work extends the multiple scattering theory to larger primary particles using the Rayleigh-Gans-Debye theory and adds the scattering from layers of varying thickness adsorbed on the primary particles to more realistically predict the effects of condensed PAH's in combustion diagnostics and the effect of condensed water and condensed hydrocarbons in atmospheric obscuration calculations. Allowance of the effect of the condensed layers on soot is important in both interpreting data on the attenuation coefficient of soot made at ambient temperatures and in predicting the impact of soot on the radiative forcing function in global climate models.