Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers
Optical trapping combined with Mie spectroscopy is a new technique used to record the refractive index of insoluble organic material extracted from atmospheric aerosol samples over a wide wavelength range. The refractive index of the insoluble organic extracts was shown to follow a Cauchy equation b...
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ftdoajarticles:oai:doaj.org/article:0620e7e489bf492e833a8f7ff55f7c0a 2023-05-15T13:35:08+02:00 Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers R. H. Shepherd M. D. King A. A. Marks N. Brough A. D. Ward 2018-04-01T00:00:00Z https://doi.org/10.5194/acp-18-5235-2018 https://doaj.org/article/0620e7e489bf492e833a8f7ff55f7c0a EN eng Copernicus Publications https://www.atmos-chem-phys.net/18/5235/2018/acp-18-5235-2018.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-18-5235-2018 1680-7316 1680-7324 https://doaj.org/article/0620e7e489bf492e833a8f7ff55f7c0a Atmospheric Chemistry and Physics, Vol 18, Pp 5235-5252 (2018) Physics QC1-999 Chemistry QD1-999 article 2018 ftdoajarticles https://doi.org/10.5194/acp-18-5235-2018 2022-12-31T00:55:52Z Optical trapping combined with Mie spectroscopy is a new technique used to record the refractive index of insoluble organic material extracted from atmospheric aerosol samples over a wide wavelength range. The refractive index of the insoluble organic extracts was shown to follow a Cauchy equation between 460 and 700 nm for organic aerosol extracts collected from urban (London) and remote (Antarctica) locations. Cauchy coefficients for the remote sample were for the Austral summer and gave the Cauchy coefficients of A = 1.467 and B = 1000 nm 2 with a real refractive index of 1.489 at a wavelength of 589 nm. Cauchy coefficients for the urban samples varied with season, with extracts collected during summer having Cauchy coefficients of A = 1.465 ± 0.005 and B = 4625 ± 1200 nm 2 with a representative real refractive index of 1.478 at a wavelength of 589 nm, whilst samples extracted during autumn had larger Cauchy coefficients of A = 1.505 and B = 600 nm 2 with a representative real refractive index of 1.522 at a wavelength of 589 nm. The refractive index of absorbing aerosol was also recorded. The absorption Ångström exponent was determined for woodsmoke and humic acid aerosol extract. Typical values of the Cauchy coefficient for the woodsmoke aerosol extract were A = 1.541 ± 0.03 and B = 14 800 ± 2900 nm 2 , resulting in a real refractive index of 1.584 ± 0.007 at a wavelength of 589 nm and an absorption Ångström exponent of 8.0. The measured values of refractive index compare well with previous monochromatic or very small wavelength range measurements of refractive index. In general, the real component of the refractive index increases from remote to urban to woodsmoke. A one-dimensional radiative-transfer calculation of the top-of-the-atmosphere albedo was applied to model an atmosphere containing a 3 km thick layer of aerosol comprising pure water, pure insoluble organic aerosol, or an aerosol consisting of an aqueous core with an insoluble organic shell. The calculation demonstrated that the ... Article in Journal/Newspaper Antarc* Antarctica Directory of Open Access Journals: DOAJ Articles Austral Atmospheric Chemistry and Physics 18 8 5235 5252 |
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English |
topic |
Physics QC1-999 Chemistry QD1-999 |
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Physics QC1-999 Chemistry QD1-999 R. H. Shepherd M. D. King A. A. Marks N. Brough A. D. Ward Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
topic_facet |
Physics QC1-999 Chemistry QD1-999 |
description |
Optical trapping combined with Mie spectroscopy is a new technique used to record the refractive index of insoluble organic material extracted from atmospheric aerosol samples over a wide wavelength range. The refractive index of the insoluble organic extracts was shown to follow a Cauchy equation between 460 and 700 nm for organic aerosol extracts collected from urban (London) and remote (Antarctica) locations. Cauchy coefficients for the remote sample were for the Austral summer and gave the Cauchy coefficients of A = 1.467 and B = 1000 nm 2 with a real refractive index of 1.489 at a wavelength of 589 nm. Cauchy coefficients for the urban samples varied with season, with extracts collected during summer having Cauchy coefficients of A = 1.465 ± 0.005 and B = 4625 ± 1200 nm 2 with a representative real refractive index of 1.478 at a wavelength of 589 nm, whilst samples extracted during autumn had larger Cauchy coefficients of A = 1.505 and B = 600 nm 2 with a representative real refractive index of 1.522 at a wavelength of 589 nm. The refractive index of absorbing aerosol was also recorded. The absorption Ångström exponent was determined for woodsmoke and humic acid aerosol extract. Typical values of the Cauchy coefficient for the woodsmoke aerosol extract were A = 1.541 ± 0.03 and B = 14 800 ± 2900 nm 2 , resulting in a real refractive index of 1.584 ± 0.007 at a wavelength of 589 nm and an absorption Ångström exponent of 8.0. The measured values of refractive index compare well with previous monochromatic or very small wavelength range measurements of refractive index. In general, the real component of the refractive index increases from remote to urban to woodsmoke. A one-dimensional radiative-transfer calculation of the top-of-the-atmosphere albedo was applied to model an atmosphere containing a 3 km thick layer of aerosol comprising pure water, pure insoluble organic aerosol, or an aerosol consisting of an aqueous core with an insoluble organic shell. The calculation demonstrated that the ... |
format |
Article in Journal/Newspaper |
author |
R. H. Shepherd M. D. King A. A. Marks N. Brough A. D. Ward |
author_facet |
R. H. Shepherd M. D. King A. A. Marks N. Brough A. D. Ward |
author_sort |
R. H. Shepherd |
title |
Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
title_short |
Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
title_full |
Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
title_fullStr |
Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
title_full_unstemmed |
Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
title_sort |
determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://doi.org/10.5194/acp-18-5235-2018 https://doaj.org/article/0620e7e489bf492e833a8f7ff55f7c0a |
geographic |
Austral |
geographic_facet |
Austral |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_source |
Atmospheric Chemistry and Physics, Vol 18, Pp 5235-5252 (2018) |
op_relation |
https://www.atmos-chem-phys.net/18/5235/2018/acp-18-5235-2018.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-18-5235-2018 1680-7316 1680-7324 https://doaj.org/article/0620e7e489bf492e833a8f7ff55f7c0a |
op_doi |
https://doi.org/10.5194/acp-18-5235-2018 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
18 |
container_issue |
8 |
container_start_page |
5235 |
op_container_end_page |
5252 |
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1766061357045645312 |