A diethylene glycol condensation particle counter for rapid sizing of sub-3nm atmospheric clusters

This article describes the modification of a laminar flow, thermally diffusive universal-fluid condensation particle counter (standard operation: 50% detection efficiency at 5nm) to rapidly measure the size distribution of sub 3nm aerosol. Sub 3nm detection was achieved by using diethylene glycol as the working fluid, which enabled high instrument super-saturations while minimizing homogenous nucleation of the working fluid; a detection efficiency of 50% was achieved at 1.6nm with laboratory-generated ammonium sulfate (AS) aerosol. Rapid aerosol sizing beneath 3nm was achieved by inverting the measured grown droplet size distribution (1s sampling) to recover the sampled aerosol size distribution. The developed inversion algorithm utilizes analytical kernel functions determined from the instrument response to pseudo-monodisperse AS aerosol from 1.5nm to 20nm, generated by a high-resolution DMA and a nano DMA. The inversion algorithm was tested numerically with assumed, idealized aerosol size distributions consistent with observed new particle formation events, yielding a reasonable agreement between inverted and assumed aerosol size distributions below 3nm. This technique provides a measure of the aerosol size assuming an aerosol composition identical to that of the aerosol used to generate the experimentally determined kernel function.Copyright (c) 2018 American Association for Aerosol Research