The diameter of soot primary particles and the soot mass concentration are measured using a laser-induced incandescence (LII) system has recently been developed in our lab. LII involves heating particles with a laser and measuring the resulting radiative emission. The magnitude of the LII signal is correlated with the volume fraction of particles in the detection region, and the decay rate of the LII signal is mainly governed by the specific surface of the particles, which in turn depends on primary particle size .
1. C. R. Shaddix and K. C. Smyth, “Laser-induced incandescence measurements of soot production in steady and flickering methane, propane, and ethylene diffusion flames,” Combust. Flame, vol. 107, pp. 418-452, 1996