High resolution characterization of a sheathed axisymmetric variable supersaturation condensation particle sizer

Abstract

Diffusive condensation particle counters (CPCs) injecting the aerosol near the symmetry axis within a larger flow of a vapor-containing sheath gas have previously exhibited a size resolving power considerably lower than theoretically expected. We hypothesize that reexamining these instruments with particles of improved uniformity in composition, size and shape should reveal a much better performance, well suited for high resolution particle sizing and basic heterogeneous nucleation studies. Accordingly, we investigate the performance of the Variable Supersaturation Condensation Particle Sizer (VSCPS) of Gallar et al. (2006) with an aerosol of uniform singly charged polyethylene glycol particles (3–9 nm diameter), produced by a bipolar electrospray, and size-selected by a differential mobility analyzer of high resolution. The condensation size resolution obtained with n-butanol vapor almost triples that previously demonstrated for this instrument, exceeds that established for any other CPC, and can apparently be further increased. Flow and temperature field calculations of the maximal supersaturation in the VSCPS would enable basic heterogeneous nucleation studies, as well as high resolution sizing of neutral or charged particles.