On the derivation of particle nucleation rates from experimental formation rates

Abstract

Particle formation rates are usually measured at sizes larger than the critical size at which nucleation occurs. Due to loss of particles during their growth to the detection threshold, the measured formation rate is often substantially lower than the nucleation rate. For this reason a correction needs to be applied in order to determine the nucleation rate from the measured formation rate. Analytical formulae for the correction factor are provided in the literature. However, these methods were derived for atmospheric nucleation measurements and therefore need to be adjusted in order to be applied to chamber nucleation studies. Here we propose an alternative, numerical method that allows precise nucleation rates to be determined in arbitrary experimental environments. The method requires knowledge of the particle size distribution above detection threshold, the particle growth rate, and the particle loss rates as a function of particle size. The effect of self-coagulation, i.e., cluster–cluster collisions, is taken into account in the method.