  The effect of optical radiation on the rate of aggregation of nanoscopic
particles is studied in metal aerosols. It has been shown that under light
exposure, polydisperse metal aerosols can aggregate up to two orders faster due
to the size dependent photoelectron effect from nanoparticles. Different size
nanoparticles undergo mutual heteropolar charging when exchanging
photoelectrons through the interparticle medium to result in an increased rate
of aggregation. It is shown that long-range electrostatic attractive forces
drive the particles into closer distances where the short-range Van-der-Waals
forces become dominating. Attention is drawn to the fact that this effect may
occur in various types of dispersed systems as well as in natural
heteroaerosols.
