In situ evaluation of the soot refractive index in the UV-visible from the measurement of the scattering and extinction coefficients in rich flames

This article proposes a new method for the evaluation of the dispersion of the optical properties of absorbing submicronic aerosols, starting from the simultaneous measurements of the scattering and extinction coefficients in the near UV and visible. The experiments were on premixed flat flames at atmospheric pressure with such nonaromatic fuels as CH4, C2H4, and C2H2 and different C-O ratios and flow rates. A quantitative determination of the special behavior of the real and imaginary parts of the complex refractive index of soot was obtained in conditions where the molecular contribution could be neglected and where the particles were not agglomerated and behaved as Rayleigh scatterers. (Edited author abstract).