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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>8</volume_number>
		<issue_number>6</issue_number>
		<publication_year>2008</publication_year>
	</journal>
	<doi>10.5194/acpd-8-20839-2008</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/8/20839/2008/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/8/20839/2008/acpd-8-20839-2008.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/8/20839/2008/acpd-8-20839-2008.pdf</fulltext_pdf>
	<start_page>20839</start_page>
	<end_page>20867</end_page>
	<publication_date>2008-12-12</publication_date>
	<article_title content_type="html">Towards closing the gap between hygroscopic growth and activation  for secondary organic aerosol â€“ Part 2: Theoretical approaches</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>M. D. Petters</name>
			<email>petters@atmos.colostate.edu</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>H. Wex</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>C. M. Carrico</name>
		</author>
		<author numeration="4" affiliations="2">
			<name>E. Hallbauer</name>
		</author>
		<author numeration="5" affiliations="2,3">
			<name>A. Massling</name>
		</author>
		<author numeration="6" affiliations="1,4">
			<name>G. R. McMeeking</name>
		</author>
		<author numeration="7" affiliations="2">
			<name>L. Poulain</name>
		</author>
		<author numeration="8" affiliations="2">
			<name>Z. Wu</name>
		</author>
		<author numeration="9" affiliations="1">
			<name>S. M. Kreidenweis</name>
		</author>
		<author numeration="10" affiliations="2">
			<name>F. Stratmann</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA</affiliation>
		<affiliation numeration="2" content_type="html">Institute for Tropospheric Research, Leipzig, Germany</affiliation>
		<affiliation numeration="3" content_type="html">now at: National Environmental Research Institute, Aarhus University, Roskilde, Denmark</affiliation>
		<affiliation numeration="4" content_type="html">now at: Centre for Atmospheric Science, University of Manchester, Manchester, UK</affiliation>
	</affiliations>
	<abstract content_type="html">We examine the hygroscopic properties of secondary organic aerosol
      particles generated through the reaction of alpha-pinene and ozone
      using a continuous flow reaction chamber. The water activity versus
      composition relationship is calculated from measurements of growth
      factors at relative humidities up to 99.6% and from measurements of
      cloud condensation nuclei activity. The observed relationships are
      complex, suggesting highly non-ideal behavior for aerosol water
      contents at relative humidities less than 98%. We present two
      models that may explain the observed water activity-composition
      relationship equally well. The first model assumes that the aerosol is
      a pseudo binary mixture of infinitely water soluble compounds and
      sparingly soluble compounds that gradually enter the solution as
      dilution increases. The second model is used to compute the Gibbs free
      energy of the aerosol-water mixture and shows that the aerosol behaves
      similarly to what can be expected for single compounds that contain
      a certain fraction of oxygenated and non-polar functional groups.</abstract>
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</article>

