Dynamic Light Scattering Study of Carbon Nanoparticles Aggregating in Aerosol Phase

Intensity correlation function was measured using ALV5000 correlator for the aerosol system created inside an optical chamber by exploding a mixture of a hydrocarbon (Acetylene) and oxygen. The observations were taken at two $q$ (scattering wave vector) values 8.81 $\mu $m$^{-1}$ and 24.20 $\mu $m$^{-1}$, which for \textit{$\lambda $} = 488nm correspond to scattering angles 40$^{o}$ and 140$^{o}$ respectively. For a system with medium volume fractions ($\sim $ 8 x 10$^{-5})$ or higher it was observed that the decay in intensity correlation was exponential initially for up to about 1 minute and then transited to stretched exponential with stretched exponent of about 0.45 for $q$ = 24.20 $\mu $m$^{-1}$and 0.65 for $q$ = 8.81 $\mu $m$^{-1}$. The value of intensity correlation function at small time is also found to decrease a little bit with time at both $q$. This indicates of the development of static scatterer in the scattering volume with time (gelling of the cluster). This also introduced non-ergodicity in the system.