On the potential of Cluster Ion Counter (CIC) to observe local new particle formation, condensation sink and growth rate of newly formed particles

Abstract. Cluster Ion Counter (CIC) is a simple 3-channel instrument designed to observe ions in the diameter range from 1.0 to 5 nm. With the three channels, we can observe concentrations of both ion clusters (sub-2 nm ions) and intermediate ions. Furthermore, as derived here, we can estimate condensation sink, intensity of local new particle formation, growth rate of newly formed particles from 2 nm to 3 nm, and formation rate of 2 nm ions. We compared CIC measurements with those of a multichannel ion spectrometer, the Neutral cluster and Air Ion Spectrometer (NAIS), and found that the concentrations agreed well between the two instruments, with the correlation coefficients of 0.89 and 0.86 for sub-2 nm and 2.0‒2.3 nm ions, respectively. According to the observations made in Hyytiälä, Finland and Beijing, China, the ion source rate was estimated to be about 2‒4 ion pairs cm‒3 s‒1.