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Complex refractive index of secondary organic aerosol generated from isoprene/NO x photooxidation in the presence and absence of SO 2
Author(s) -
Nakayama Tomoki,
Sato Kei,
Tsuge Masashi,
Imamura Takashi,
Matsumi Yutaka
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023522
Subject(s) - isoprene , aerosol , refractive index , chromophore , chemistry , wavelength , photochemistry , ultraviolet , analytical chemistry (journal) , absorption (acoustics) , conjugated system , carbon black , materials science , organic chemistry , optoelectronics , polymer , copolymer , composite material , natural rubber
We report the first measurements of the complex refractive index (RI) at 375, 405, 532, and 781 nm for secondary organic aerosol (SOA) generated from isoprene/NO x photooxidation. At all wavelengths studied, slightly greater real components of the RI were observed for the SOA generated in the absence of SO 2 compared with those generated in its presence. Considering the chemical properties, the differences in the oxidation state and/or ratio of particle density to molecular weight of compounds in the SOA are considered to be the main factors determining the real components. The imaginary components at ≤532 nm were found to increase with increasing initial SO 2 concentration. The highly conjugated oligomers are suggested to be plausible chromophore candidates. This study suggests that when large amounts of SOA are generated after mixing of isoprene with NO x and SO x , light absorption of these SOAs may compete with that of black carbon, especially at ultraviolet wavelengths.