Extinction efficiencies of coated absorbing aerosols measured by cavity ring down aerosol spectrometry A. Abo Riziq1, M. Trainic1, C. Erlick2, E. Segre3, and Y. Rudich1 1Department of Environmental Sciences, Weizmann Institute, Rehovot, 76100, Israel 2Department of Atmospheric Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel 3Physics Services, Weizmann Institute, Rehovot, 76100, Israel
Abstract. In this study, we measure the extinction efficiency at 532 nm of absorbing
aerosol particles coated with a non-absorbing solid and liquid organic shell
with coating thickness varying between 5 and 100 nm using cavity ring down
aerosol spectrometry. For this purpose, we use nigrosin, an organic black
dye, as a model absorbing core and two non-absorbing organic substances as
shells, glutaric acid (GA) and Di-Ethyl-Hexyl-Sebacate (DEHS). The measured
behavior of the coated particles is consistent with Mie
calculations of core-shell particles. Errors between measured and calculated
values for nigrosin coated with GA and DEHS are between 0.5% and 10.5%
and between 0.5% and 9%, respectively. However, it is evident that the
calculations are in better agreement with the measured results for thinner
coatings. Possible reasons for these discrepancies are discussed.
Citation: Abo Riziq, A., Trainic, M., Erlick, C., Segre, E., and Rudich, Y.: Extinction efficiencies of coated absorbing aerosols measured by cavity ring down aerosol spectrometry, Atmos. Chem. Phys., 8, 1823-1833, doi:10.5194/acp-8-1823-2008, 2008.