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| Titel |
Optical properties of absorbing and non-absorbing aerosols retrieved by cavity ring down (CRD) spectroscopy |
| VerfasserIn |
A. Abo Riziq, C. Erlick, E. Dinar, Y. Rudich |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 6 ; Nr. 7, no. 6 (2007-03-21), S.1523-1536 |
| Datensatznummer |
250004826
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| Publikation (Nr.) |
 copernicus.org/acp-7-1523-2007.pdf |
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| Zusammenfassung |
| Application of cavity ring down (CRD) spectrometry for measuring the optical
properties of pure and mixed laboratory-generated aerosols is presented. The
extinction coefficient (αext), extinction cross section
(σext) and extinction efficiency (Qext) were measured for
polystyrene spheres (PSS), ammonium sulphate ((NH4)2(SO4),
sodium chloride (NaCl), glutaric acid (GA), and Rhodamine-590 aerosols. The
refractive indices of the different aerosols were retrieved by comparing the
measured extinction efficiency of each aerosol type to the extinction
predicted by Mie theory. Aerosols composed of sodium chloride and glutaric
acid in different mixing ratios were used as model for mixed aerosols of two
non-absorbing materials, and their extinction and complex refractive index
were derived. Aerosols composed of Rhodamine-590 and ammonium sulphate in
different mixing ratios were used as model for mixing of absorbing and
non-absorbing species, and their optical properties were derived. The
refractive indices of the mixed aerosols were also calculated by various
optical mixing rules. We found that for
non-absorbing mixtures, the linear rule, Maxwell-Garnett rule, and extended
effective medium approximation (EEMA), give
comparable results, with the linear mixing rule giving a slightly better fit
than the others. Overall, calculations for the mixed aerosols are not as
good as for single component aerosols. For absorbing mixtures, the
differences between the refractive indices calculated using the mixing rules
and those retrieved by CRD are generally higher. |
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