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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-10-7617-2010</article-id>
<title-group>
<article-title>High variability of the heterogeneous ice nucleation potential of oxalic acid dihydrate and sodium oxalate</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wagner</surname>
<given-names>R.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Möhler</surname>
<given-names>O.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Saathoff</surname>
<given-names>H.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Schnaiter</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Leisner</surname>
<given-names>T.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Karlsruhe, Germany</addr-line>
</aff>
<pub-date pub-type="epub">
<day>16</day>
<month>08</month>
<year>2010</year>
</pub-date>
<volume>10</volume>
<issue>16</issue>
<fpage>7617</fpage>
<lpage>7641</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<self-uri xlink:href="http://www.atmos-chem-phys.net/10/7617/2010/acp-10-7617-2010.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/7617/2010/acp-10-7617-2010.pdf</self-uri>
<abstract>
<p>The heterogeneous ice nucleation potential of airborne oxalic acid dihydrate
and sodium oxalate particles in the deposition and condensation mode has
been investigated by controlled expansion cooling cycles in the AIDA aerosol
and cloud chamber of the Karlsruhe Institute of Technology at temperatures
between 244 and 228 K. Previous laboratory studies have highlighted the
particular role of oxalic acid dihydrate as the only species amongst a
variety of other investigated dicarboxylic acids to be capable of acting as
a heterogeneous ice nucleus in both the deposition and immersion mode. We
could confirm a high deposition mode ice activity for 0.03 to 0.8 μm
sized oxalic acid dihydrate particles that were either formed by nucleation
from a gaseous oxalic acid/air mixture or by rapid crystallisation of highly
supersaturated aqueous oxalic acid solution droplets. The critical
saturation ratio with respect to ice required for deposition nucleation was
found to be less than 1.1 and the size-dependent ice-active fraction of the
aerosol population was in the range from 0.1 to 22%. In contrast, oxalic
acid dihydrate particles that had crystallised from less supersaturated
solution droplets and had been allowed to slowly grow in a supersaturated
environment from still unfrozen oxalic acid solution droplets over a time
period of several hours were found to be much poorer heterogeneous ice
nuclei. We speculate that under these conditions a crystal surface structure
with less-active sites for the initiation of ice nucleation was generated.
Such particles partially proved to be almost ice-inactive in both the
deposition and condensation mode. At times, the heterogeneous ice nucleation
ability of oxalic acid dihydrate significantly changed when the particles
had been processed in preceding cloud droplet activation steps. Such
behaviour was also observed for the second investigated species, namely
sodium oxalate. Our experiments address the atmospheric scenario that
coating layers of oxalic acid or its salts may be formed by physical and
chemical processing on pre-existing particulates such as mineral dust and
soot. Given the broad diversity of the observed heterogeneous ice
nucleability of the oxalate species, it is not straightforward to predict
whether an oxalate coating layer will improve or reduce the ice nucleation
ability of the seed aerosol particles.</p>
</abstract>
<counts><page-count count="25"/></counts>
</article-meta>
</front>
<body/>
<back>
<ref-list>
<title>References</title>
<ref id="ref1">
<label>1</label><mixed-citation publication-type="other" xlink:type="simple"> Apelblat, A. and Manzurola, E.: Solubility of Oxalic, Malonic, Succinic, Adipic, Maleic, Malic, Citric, and Tartaric Acids in Water from 278.15 K to 338.15 K, J. Chem. Thermodyn., 19, 317–320, 1987. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple"> Archuleta, C. M., DeMott, P. J., and Kreidenweis, S. M.: Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures, Atmos. Chem. Phys., 5, 2617–2634, doi:10.5194/acp-5-2617-2005, 2005. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple"> Arnott, W. P., Dong, Y. Y., and Hallett, J.: Extinction Efficiency in the Infrared (2–18 μm) of Laboratory Ice Clouds – Observations of Scattering Minima in the Christiansen Bands of Ice, Appl. Opt., 34, 541–551, 1995. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple"> Baustian, K. J., Wise, M. E., and Tolbert, M. A.: Depositional ice nucleation on solid ammonium sulfate and glutaric acid particles, Atmos. Chem. Phys., 10, 2307–2317, doi:10.5194/acp-10-2307-2010, 2010. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple"> Bellamy, L. J. and Pace, R. J.: Hydrogen Bonding in Carboxylic Acids.1. Oxalic Acids, Spectrochim. Acta, 19, 435–442, 1963. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple"> Benz, S., Megahed, K., Möhler, O., Saathoff, H., Wagner, R., and Schurath, U.: T-dependent rate measurements of homogeneous ice nucleation in cloud droplets using a large atmospheric simulation chamber, J. Photochem. Photobiol. A, 176, 208–217, 2005. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple"> Braban, C. F., Carroll, M. F., Styler, S. A., and Abbatt, J. P. D.: Phase transitions of malonic and oxalic acid aerosols, J. Phys. Chem. A, 107, 6594–6602, 2003. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple"> Carlton, A. G., Turpin, B. J., Altieri, K. E., Seitzinger, S., Reff, A., Lim, H. J., and Ervens, B., Atmospheric oxalic acid and SOA production from glyoxal: Results of aqueous photooxidation experiments, Atmos. Env., 41, 7588–7602, 2007. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple"> Carstensen, J. T. and Dali, M., Determination of mass transfer dissolution rate constants from critical time of dissolution of a powder sample, Pharm. Dev. Technol., 4, 1–8, 1999. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple"> Carstensen, J. T. and Patel, M.: Dissolution Patterns of Polydisperse Powders – Oxalic Acid Dihydrate, J. Pharm. Sci., 64, 1770–1776, 1975. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple"> Chebbi, A. and Carlier, P.: Carboxylic acids in the troposphere, occurrence, sources, and sinks: A review, Atmos. Env., 30, 4233–4249, 1996. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple"> Clegg, S. L. and Seinfeld, J. H.: Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. 1. The acids as nondissociating components, J. Phys. Chem. A, 110, 5692–5717, 2006. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple"> Crahan, K. K., Hegg, D., Covert, D. S., and Jonsson, H.: An exploration of aqueous oxalic acid production in the coastal marine atmosphere, Atmos. Env., 38, 3757–3764, 2004. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple"> Ebisuzaki, Y. and Angel, S. M., Raman Study of Hydrogen-Bonding in Alpha and Beta Oxalic Acid Dihydrate, J. Raman Spectrosc., 11, 306–311, 1981. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple"> Echle, G., von Clarmann, T., and Oelhaf, H.: Optical and microphysical parameters of the Mt. Pinatubo aerosol as determined from MIPAS-B mid-IR limb emission spectra, J. Geophys. Res. Atmos., 103, 19193–19211, 1998. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple"> Edwards, G. R. and Evans, L. F.: The Mechanism of Activation of Ice Nuclei, J. Atmos. Sci., 28, 1443–1447, 1971. </mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple"> Ervens, B., Feingold, G., Frost, G. J., and Kreidenweis, S. M.: A modeling study of aqueous production of dicarboxylic acids: 1. Chemical pathways and speciated organic mass production, J. Geophys. Res. Atmos., 109, D15205, doi:10.1029/2003JD004387, 2004. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple"> Evans, L. F.: Ice Nucleation under Pressure and in Salt Solution, Trans. Faraday Soc., 63, 3060–3071, 1967. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple"> Fukuta, N.: Activation of Atmospheric Particles as Ice Nuclei in Cold and Dry Air, J. Atmos. Sci., 23, 741–750, 1966. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple"> Hartman, K. O. and Hisatsune, I. C.: The Kinetics of Oxalate Ion Pyrolysis in a Potassium Bromide Matrix, J. Phys. Chem., 71, 392–396, 1967. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple"> Higuchi, K. and Fukuta, N.: Ice in Capillaries of Solid Particles and Its Effect on Their Nucleating Ability, J. Atmos. Sci., 23, 187–190, 1966. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple"> Hinds, W. C.: Aerosol Technology, John Wiley &amp; Sons, Inc., New York, USA, Chapter 3, 42–74, 1999. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple"> Hsieh, L. Y., Kuo, S. C., Chen, C. L., and Tsai, Y. I.: Origin of low-molecular-weight dicarboxylic acids and their concentration and size distribution variation in suburban aerosol, Atmos. Env., 41, 6648–6661, 2007. </mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple"> Hudson, P. K., Gibson, E. R., Young, M. A., Kleiber, P. D., and Grassian, V. H.: A newly designed and constructed instrument for coupled infrared extinction and size distribution measurements of aerosols, Aerosol. Sci. Tech., 41, 701–710, 2007. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple"> Kanji, Z. A. and Abbatt, J. P. D.: Laboratory studies of ice formation via deposition mode nucleation onto mineral dust and n-hexane soot samples, J. Geophys. Res. Atmos., 111, D16204, doi:10.1029/2005JD006766, 2006. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple"> Kanji, Z. A., Florea, O., and Abbatt, J. P. D.: Ice formation via deposition nucleation on mineral dust and organics: dependence of onset relative humidity on total particulate surface area, Environ. Res. Lett., 3, 025004, doi:10.1088/1748-9326/3/2/025004, 2008. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple"> Kawamura, K., Kasukabe, H., and Barrie, L. A., Source and reaction pathways of dicarboxylic acids, ketoacids and dicarbonyls in arctic aerosols: One year of observations, Atmos. Environ., 30, 1709–1722, 1996. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple"> Kerminen, V. M., Ojanen, C., Pakkanen, T., Hillamo, R., Aurela, M., and Merilainen, J.: Low-molecular-weight dicarboxylic acids in an urban and rural atmosphere, J. Aerosol Sci., 31, 349–362, 2000. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple"> Kerminen, V. M., Teinila, K., Hillamo, R., and Makela, T.: Size-segregated chemistry of particulate dicarboxylic acids in the Arctic atmosphere, Atmos. Env., 33, 2089–2100, 1999. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple"> Limbeck, A., Kraxner, Y., and Puxbaum, H.: Gas to particle distribution of low molecular weight dicarboxylic acids at two different sites in central Europe (Austria), J. Aerosol Sci., 36, 991–1005, 2005. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple"> Marcolli, C., Gedamke, S., Peter, T., and Zobrist, B.: Efficiency of immersion mode ice nucleation on surrogates of mineral dust, Atmos. Chem. Phys., 7, 5081–5091, doi:10.5194/acp-7-5081-2007, 2007. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple"> Mikhailov, E., Vlasenko, S., Martin, S. T., Koop, T., and Pöschl, U., Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations, Atmos. Chem. Phys., 9, 9491–9522, doi:10.5194/acp-9-9491-2009, 2009. </mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple"> Mishchenko, M. I., Travis, L. D., and Mackowski, D. W.: T-matrix computations of light scattering by nonspherical particles: A review, J. Q. Spectrosc. Radiat. Transfer, 55, 535–575, 1996. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple"> Möhler, O., Benz, S., Saathoff, H., Schnaiter, M., Wagner, R., Schneider, J., Walter, S., Ebert, V., and Wagner, S.: The effect of organic coating on the heterogeneous ice nucleation efficiency of mineral dust aerosols, Environ. Res. Letters, 3, 025007, doi:10.1088/1748-9326/3/2/025007, 2008. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple"> Möhler, O., Büttner, S., Linke, C., Schnaiter, M., Saathoff, H., Stetzer, O., Wagner, R., Krämer, M., Mangold, A., Ebert, V., and Schurath, U.: Effect of Sulphuric Acid Coating on Heterogeneous Ice Nucleation by Soot Aerosol Particles, J. Geophys. Res. Atmos., 110, D11210, doi:10.1029/2004JD005169, 2005. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple"> Möhler, O., Field, P. R., Connolly, P., Benz, S., Saathoff, H., Schnaiter, M., Wagner, R., Cotton, R., Krämer, M., Mangold, A., and Heymsfield, A. J.: Efficiency of the deposition mode ice nucleation on mineral dust particles, Atmos. Chem. Phys., 6, 3007–3021, doi:10.5194/acp-6-3007-2006, 2006. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple"> Mossop, S. C.: Sublimation Nuclei, P. Phys. Soc. Lond. B, 69, 161–164, 1956. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple"> Murphy, D. M. and Koop, T.: Review of the vapour pressures of ice and supercooled water for atmospheric applications, Q. J. Roy. Meteorol. Soc., 131, 1539–1565, 2005. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple"> Murray, B. J., Wilson, T. W., Dobbie, S., Cui, Z., Al-Jumur, S. M. R. K., Möhler, O., Schnaiter, M., Wagner, R., Benz, S., Niemand, M., Saathoff, H., Ebert, V., Wagner, S., and Kärcher, B.: Heterogeneous nucleation of ice particles on glassy aerosols under cirrus conditions, Nat. Geosci., 3, 233–237, 2010. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple"> Omar, W. and Ulrich, J.: Solid liquid equilibrium, metastable zone, and nucleation parameters of the oxalic acid-water system, Cryst. Growth Des., 6, 1927–1930, 2006. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple"> Parsons, M. T., Mak, J., Lipetz, S. R., and Bertram, A. K., Deliquescence of malonic, succinic, glutaric, and adipic acid particles, J. Geophys. Res. Atmos., 109, D06212, doi:10.1029/2003JD004075, 2004. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple"> Peng, C., Chan, M. N., and Chan, C. K.: The hygroscopic properties of dicarboxylic and multifunctional acids: Measurements and UNIFAC predictions, Environ. Sci. Technol., 35, 4495–4501, 2001. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple"> Peng, C. G. and Chan, C. K.: The water cycles of water-soluble organic salts of atmospheric importance, Atmos. Environ., 35, 1183–1192, 2001. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple"> Prenni, A. J., DeMott, P. J., Kreidenweis, S. M., Sherman, D. E., Russell, L. M., and Ming, Y.: The effects of low molecular weight dicarboxylic acids on cloud formation, J. Phys. Chem. A, 105, 11240–11248, 2001. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple"> Pruppacher, H. R. and Klett, J. D.: Microphysics of Clouds and Precipitation, Kluwer Acacdemic Publishers, Dordrecht, The Netherlands, 326–341, 1997. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple"> Roberts, P. and Hallett, J.: A Laboratory Study of Ice Nucleating Properties of Some Mineral Particulates, Q. J. Roy. Meteorol. Soc., 94, 25–34, 1968. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple"> Shilling, J. E., Fortin, T. J., and Tolbert, M. A.: Depositional ice nucleation on crystalline organic and inorganic solids, J. Geophys. Res. Atmos., 111, D12204, doi:10.1029/2005JD006664, 2006. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple"> Torgesen, J. L. and Strassburger, J.: Growth of Oxalic Acid Single Crystals from Solution – Solvent Effects on Crystal Habit, Science, 146, 53–55, 1964. </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple"> Treuel, L., Schulze, S., Leisner, T., and Zellner, R., Deliquescence behaviour of single levitated ternary salt/carboxylic acid/water microdroplets, Faraday Discuss., 137, 265–278, 2008. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple"> Vali, G.: Repeatability and randomness in heterogeneous freezing nucleation, Atmos. Chem. Phys., 8, 5017–5031, doi:10.5194/acp-8-5017-2008, 2008. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple"> Villepin, J. D. and Novak, A.: Vibration-Spectra of Oxalic Acids.1. Infrared and Raman-Spectra of Beta-Phase of Some Acids, Spectrochim. Acta A, 34, 1009–1017, 1978a. </mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple"> Villepin, J. D. and Novak, A.: Vibration-Spectra of Oxalic Acids.2. Infrared and Raman-Spectra of Alpha-Phase of Some Acids, Spectrochim. Acta A, 34, 1019–1024, 1978b. </mixed-citation>
</ref>
<ref id="ref53">
<label>53</label><mixed-citation publication-type="other" xlink:type="simple"> Wagner, R., Benz, S., Bunz, H., Möhler, O., Saathoff, H., Schnaiter, M., Leisner, T., and Ebert, V.: Infrared Optical Constants of Highly Diluted Sulfuric Acid Solution Droplets at Cirrus Temperatures, J. Phys. Chem. A, 112, 11661–11676, 2008. </mixed-citation>
</ref>
<ref id="ref54">
<label>54</label><mixed-citation publication-type="other" xlink:type="simple"> Wagner, R., Benz, S., Möhler, O., Saathoff, H., Schnaiter, M., and Schurath, U.: Mid-infrared extinction spectra and optical constants of supercooled water droplets, J. Phys. Chem. A, 109, 7099–7112, 2005a. </mixed-citation>
</ref>
<ref id="ref55">
<label>55</label><mixed-citation publication-type="other" xlink:type="simple"> Wagner, R., Benz, S., Möhler, O., Saathoff, H., and Schurath, U.: Probing ice clouds by broadband mid-infrared extinction spectroscopy: case studies from ice nucleation experiments in the AIDA aerosol and cloud chamber, Atmos. Chem. Phys., 6, 4775–4800, doi:10.5194/acp-6-4775-2006, 2006. </mixed-citation>
</ref>
<ref id="ref56">
<label>56</label><mixed-citation publication-type="other" xlink:type="simple"> Wagner, R., Linke, C., Naumann, K. H., Schnaiter, M., Vragel, M., Gangl, M., and Horvath, H.: A review of optical measurements at the aerosol and cloud chamber AIDA, J. Quant. Spectrosc. Radiat. Transfer, 110, 930–949, 2009. </mixed-citation>
</ref>
<ref id="ref57">
<label>57</label><mixed-citation publication-type="other" xlink:type="simple"> Wagner, R., Möhler, O., Saathoff, H., Stetzer, O., and Schurath, U.: Infrared spectrum of nitric acid dihydrate – influence of particle shape, J. Phys. Chem. A, 109, 2572–2581, 2005b. </mixed-citation>
</ref>
<ref id="ref58">
<label>58</label><mixed-citation publication-type="other" xlink:type="simple"> Wenger, M. and Bernstein, J.: Cocrystal design gone awry? A new dimorphic hydrate of oxalic acid, Mol. Pharm., 4, 355–359, 2007. </mixed-citation>
</ref>
<ref id="ref59">
<label>59</label><mixed-citation publication-type="other" xlink:type="simple"> Yang, F., Chen, H., Wang, X. N., Yang, X., Du, J. F., and Chen, J. M.: Single particle mass spectrometry of oxalic acid in ambient aerosols in Shanghai: Mixing state and formation mechanism, Atmos. Environ., 43, 3876–3882, 2009. </mixed-citation>
</ref>
<ref id="ref60">
<label>60</label><mixed-citation publication-type="other" xlink:type="simple"> Yao, X. H., Fang, M., and Chan, C. K.: Size distributions and formation of dicarboxylic acids in atmospheric particles, Atmos. Environ., 36, 2099–2107, 2002. </mixed-citation>
</ref>
<ref id="ref61">
<label>61</label><mixed-citation publication-type="other" xlink:type="simple"> Zakharova, N. T. and Mishchenko, M. I.: Scattering properties of needlelike and platelike ice spheroids with moderate size parameters, Appl. Opt., 39, 5052–5057, 2000. </mixed-citation>
</ref>
<ref id="ref62">
<label>62</label><mixed-citation publication-type="other" xlink:type="simple"> Zasetsky, A. Y., Khalizov, A. F., Earle, M. E., and Sloan, J. J.: Frequency Dependent Complex Refractive Indices of Supercooled Liquid Water and Ice Determined from Aerosol Extinction Spectra, J. Phys. Chem. A, 109, 2760–2764, 2005. </mixed-citation>
</ref>
<ref id="ref63">
<label>63</label><mixed-citation publication-type="other" xlink:type="simple"> Zobrist, B., Marcolli, C., Koop, T., Luo, B. P., Murphy, D. M., Lohmann, U., Zardini, A. A., Krieger, U. K., Corti, T., Cziczo, D. J., Fueglistaler, S., Hudson, P. K., Thomson, D. S., and Peter, T.: Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect, Atmos. Chem. Phys., 6, 3115–3129, doi:10.5194/acp-6-3115-2006, 2006. </mixed-citation>
</ref>
<ref id="ref64">
<label>64</label><mixed-citation publication-type="other" xlink:type="simple"> Zobrist, B., Marcolli, C., Pedernera, D. A., and Koop, T.: Do atmospheric aerosols form glasses?, Atmos. Chem. Phys., 8, 5221–5244, doi:10.5194/acp-8-5221-2008, 2008. </mixed-citation>
</ref>
<ref id="ref65">
<label>65</label><mixed-citation publication-type="other" xlink:type="simple"> Zuberi, B., Bertram, A. K., Koop, T., Molina, L. T., and Molina, M. J.: Heterogeneous freezing of aqueous particles induced by crystallized (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;, ice, and letovicite, J. Phys. Chem. A, 105, 6458–6464, 2001. </mixed-citation>
</ref>
</ref-list>
</back>
</article>