  We report a theoretical analysis showing that Rayleigh scattering could be
used to monitor the growth of nanoparticles under arc discharge conditions. We
compute the Rayleigh scattering cross sections of the nanoparticles by
combining light scattering theory for gas-particle mixtures with calculations
of the dynamic electronic polarizability of the nanoparticles. We find that the
resolution of the Rayleigh scattering probe is adequate to detect nanoparticles
as small as C60 at the expected concentrations of synthesis conditions in the
arc periphery. Larger asymmetric nanoparticles would yield brighter signals,
making possible to follow the evolution of the growing nanoparticle population
from the evolution of the scattered intensity. Observable spectral features
include characteristic resonant behaviour, shape-dependent depolarization
ratio, and mass-dependent line shape. Direct observation of nanoparticles in
the early stages of growth with unobtrusive laser probes should give insight on
the particle formation mechanisms and may lead to better-controlled synthesis
protocols.
