(385f) Measurements of Newly Formed 1 – 3 Nanometer Particles Using a High Time Resolution Nanoparticle Size Spectrometer

New particle formation (NPF) by photochemical reactions of gas-phase precursors significantly enhances the number concentrations of atmospheric aerosols. These particles exert a considerable impact on global climate by affecting the earth's radiation balance directly through their scattering of incoming solar radiation and indirectly through their role as potential cloud condensation nuclei. Boundary layer NPF has been frequently observed in diverse environments where nucleated particles (~ 1 nm in mobility diameter) are formed at rates that are orders of magnitude higher than predicted by early models. While methods for measuring sizes and concentrations of newly formed particles larger than 3 nanometers are well established, measurements of nanoparticles and neutral molecular clusters smaller than this are needed to constrain nucleation rates and to better understand the nucleation mechanism. To this end, a new aerosol instrument for ?bridging the gap? in measurements from neutral molecular clusters to nanoparticles has been developed, characterized, and continuously deployed in an intensive measurement campaign at Boulder, CO. This proto-type instrument consists of a newly developed oleic acid condensation particle counter for detecting aerosols with mobility diameters down to 1.2 nanometers, followed by a fast integrated mobility spectrometer (FIMS) for high time resolution (1 second) measurements of grown particle size. This instrument utilizes the controlled condensation of oleic acid to grow sampled nanoparticles, after which the sizes of the grown particles are measured by the FIMS. The unique relationship between sampled and grown particle size not only provides a means of inferring the size of nucleated particles, but also provides qualitative information regarding nucleated particle composition. Laboratory instrument characterizations and field results will be presented.