On the derivation of particle nucleation rates from experimental formation rates

Atmospheric particle formation rates are usually measured at sizes larger than the critical size where nucleation occurs. Due to loss of particles during their growth to the detection threshold, the measured formation rate is often substantially smaller 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. An analytical formula for the correction factor is provided by Kerminen and Kulmala (2002). Their method was derived for atmospheric nucleation measurements and we show here that it has limited applicability to chamber nucleation studies. The reason for this limitation is that the particle loss rate generally has a different dependency on particle size in other environments. 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.