INVERSION OF ULTRAFINE CONDENSATION NUCLEUS COUNTER PULSE-HEIGHT DISTRIBUTIONS TO OBTAIN NANOPARTICLE (SIMILAR-TO-3-10 NM) SIZE DISTRIBUTIONS

Previous work (Ahn and Liu (1990) J. Aerosol. Sci. 21, 249-261; Brockm ann (1981) Ph.D. Thesis, University of Minnesota; Rebours et al. (1992 ) J. Aerosol. Sci. 23, S189-S192; Stolzenburg (1988) Ph.D. thesis, Uni versity of Minnesota) has shown that for particles smaller than about 15 nm, pulse heights produced by the optical detector in a white-light ultrafine condensation nucleus counter (UCNC; Stolzenburg and McMurry (1991) Aerosol. Sci. 'Technol. 14, 48-65) decrease with initial parti cle size. We have previously reported on the use of pulse heights from this instrument to determine the concentrations of freshly nucleated atmospheric nanoparticles in the 3-4 nm diameter range (Weber et al. ( 1995) J. Atm. Sci. 52, 2242-2257) Weber et al. (1997) J. Geophys. Res. 102, 4375-4385). In this paper we report on the inversion of measured pulse-height distributions to obtain size distributions of particles in the 3-10 nm diameter range. Using methods developed by Stolzenburg (Stolzenburg (1988) Ph.D. Thesis, University of Minnesota) the effect of diffusional broadening is taken into account so as to obtain monodi sperse kernel functions from measured pulse-height distributions produ ced by DMA-generated calibration aerosols in the 3-50 nm diameter rang e. These kernel functions are then used with the MICRON algorithm desc ribed by Wolfenbarger and Seinfeld (1990, J. Aerosol. Sci. 21, 227-247 ) to obtain size distributions of nanoparticle aerosols from measured pulse height distributions. Calculations were done to ensure that assu med pulse-height data generated from selected known size distributions can be inverted to recover the original size distribution. Results fr om these validation studies are discussed. Applications of the inversi on algorithm to data acquired in studies of homogeneous nucleation in the atmosphere are also presented. Published by Elsevier Science Ltd.