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Temperature dependence of UV absorption cross sections and atmospheric implications of several alkyl iodides

Roehl, Coleen M. and Burkholder, James B. and Moortgat, Geert K. and Ravishankara, A. R. and Crutzen, Paul J. (1997) Temperature dependence of UV absorption cross sections and atmospheric implications of several alkyl iodides. Journal of Geophysical Research. Atmospheres, 102 (D11). pp. 12819-12829. ISSN 2169-897X. https://resolver.caltech.edu/CaltechAUTHORS:20181128-113208441

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Abstract

The ultraviolet absorption spectra of a number of alkyl iodides which have been found in the troposphere, CH_3I, C_2H_5I, CH_3CH_2CH_2I, CH_3CHICH_3, CH_2I_2, and CH2_ClI, have been measured over the wavelength range 200–380 nm and at temperatures between 298 and 210 K. The absorption spectra of the monoiodides C_H3I, C_2H_5I, CH_3CH_2CH_2I, and CH_3CHICH_3 are nearly identical in shape and magnitude and consist of single broad bands centered near 260 nm. The addition of a chlorine atom in CH_2ClI shifts its spectrum to longer wavelengths (σ_(max) at 270 nm). The spectrum of CH_2I_2 is further red‐shifted, reaching a maximum of 3.85×10^(−18) cm^2 molecule^(−1) at 288 nm and exhibiting strong absorption in the solar actinic region, λ>290 nm. Atmospheric photolysis rate constants, J values, have been calculated assuming quantum efficiencies of unity for different solar zenith angles as a function of altitude using the newly measured cross sections. Surface photolysis rate constants, calculated from the absorption cross sections measured at 298 K, range from 3×10^(−6) s^(−1) for CH)3I to 5×10^(−3) s^(−1) for CH)2I)2 at a solar zenith angle of 40°.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/97jd00530DOIArticle
ORCID:
AuthorORCID
Roehl, Coleen M.0000-0001-5383-8462
Additional Information:© 1997 by the American Geophysical Union. (Received November 14, 1996; revised February 12, 1997; accepted February 12, 1997.) Research at MPI was funded through the Max-Planck-Gesellschaft. The work at NOAA was funded in part by NASA's Upper Atmospheric Research Program.
Funders:
Funding AgencyGrant Number
Max-Planck-GesellschaftUNSPECIFIED
NASAUNSPECIFIED
Issue or Number:D11
Record Number:CaltechAUTHORS:20181128-113208441
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20181128-113208441
Official Citation:Roehl, C. M., J. B. Burkholder, G. K. Moortgat, A. R. Ravishankara, and P. J. Crutzen (1997), Temperature dependence of UV absorption cross sections and atmospheric implications of several alkyl iodides, J. Geophys. Res., 102(D11), 12819–12829, doi: 10.1029/97JD00530.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91291
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:28 Nov 2018 23:56
Last Modified:03 Oct 2019 20:33

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