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Thermal volatilization is explored as a means of inferring the chemical composition of atmospheric aerosol particles with
diameters smaller than 10 nm (nanoparticles). Such particles contain too little mass for quantitative chemical determination
by traditional analytical methods. Aerosols were subjected to increasing temperature in an oven and particle loss was measured
as a function of temperature with the TSI model 3025 ultrafine condensation particle counter (UCPC), which is capable of counting
particles with diameters as small as 3 nm. Particle nucleation was observed down stream of the oven when it was heated above
about 400°C. To reduce this artifact, the sample air down stream of the oven was cooled to condense the hot gases and/or the
freshly nucleated particles before they reached the UCPC. Controlled experiments were done with pure ammonium sulfate (NH4)2SO4 particles. The experimental design was optimized based on the known concentration of pure (NH4)2SO4 particles vaporized in the oven and the diffusion of this material to the walls of the sampling tube before the particle
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