<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd">
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="3.0" xml:lang="en">
<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>GÃ¶ttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-9-3357-2009</article-id>
<title-group>
<article-title>Hydration increases the lifetime of HSO&lt;sub&gt;5&lt;/sub&gt; and enhances its ability to act as a nucleation precursor &amp;ndash; a computational study</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>KurtÃ©n</surname>
<given-names>T.</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>Berndt</surname>
<given-names>T.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Stratmann</surname>
<given-names>F.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Physics, P.O. Box 64, 00014 University of Helsinki, Helsinki, Finland</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Leibniz-Institut fÃ¼r TroposphÃ¤renforschung e.V., Permoserstr. 15, 04318 Leipzig, Germany</addr-line>
</aff>
<pub-date pub-type="epub">
<day>25</day>
<month>05</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>10</issue>
<fpage>3357</fpage>
<lpage>3369</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>
<self-uri xlink:href="http://www.atmos-chem-phys.net/9/3357/2009/acp-9-3357-2009.html">This article is available from http://www.atmos-chem-phys.net/9/3357/2009/acp-9-3357-2009.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/9/3357/2009/acp-9-3357-2009.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/3357/2009/acp-9-3357-2009.pdf</self-uri>
<abstract>
<p>Recent experimental findings indicate that HSO&lt;sub&gt;5&lt;/sub&gt; radicals may
play a key role in the nucleation of atmospheric SO&lt;sub&gt;2&lt;/sub&gt; oxidation
products. HSO&lt;sub&gt;5&lt;/sub&gt; radicals are metastable intermediates formed in the
SO&lt;sub&gt;2&lt;/sub&gt; oxidation process, and their stability and lifetime are, at
present, highly uncertain. Previous high-level computational studies have
predicted rather low stabilities for HSO&lt;sub&gt;5&lt;/sub&gt; with respect to dissociation
into SO&lt;sub&gt;3&lt;/sub&gt;+HO&lt;sub&gt;2&lt;/sub&gt;, and have predicted the net reaction HSO&lt;sub&gt;3&lt;/sub&gt;+OH&amp;rarr;SO&lt;sub&gt;3&lt;/sub&gt;+HO&lt;sub&gt;2&lt;/sub&gt;
to be slightly exothermal. However, these studies
have not accounted for hydration of HSO&lt;sub&gt;5&lt;/sub&gt; or its precursor HSO&lt;sub&gt;3&lt;/sub&gt;. In
this study, we have estimated the effect of hydration on the stability and
lifetime of HSO&lt;sub&gt;5&lt;/sub&gt; using the advanced quantum chemical methods CCSD(T)
and G3B3. We have computed formation energies and free energies for mono-
and dihydrates of OH, HSO&lt;sub&gt;3&lt;/sub&gt;, HSO&lt;sub&gt;5&lt;/sub&gt;, SO&lt;sub&gt;3&lt;/sub&gt; and HO&lt;sub&gt;2&lt;/sub&gt;, and also
reanalyzed the individual steps of the HSO&lt;sub&gt;3&lt;/sub&gt;+O&lt;sub&gt;2&lt;/sub&gt;&amp;rarr;HSO&lt;sub&gt;5&lt;/sub&gt;&amp;rarr;SO&lt;sub&gt;3&lt;/sub&gt;+HO&lt;sub&gt;2&lt;/sub&gt; reaction at a higher level of theory than
previously published. Our results indicate that hydration is likely to
significantly prolong the lifetime of the HSO&lt;sub&gt;5&lt;/sub&gt; intermediate in
atmospheric conditions, thus increasing the probability of reactions that
form products with more than one sulfur atom. Kinetic modeling indicates
that these results may help explain the experimental observations that a
mixture of sulfur-containing products formed from SO&lt;sub&gt;2&lt;/sub&gt; oxidation by OH
radicals nucleates much more effectively than sulfuric acid taken from a
liquid reservoir.</p>
</abstract>
<counts><page-count count="13"/></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"> Aaltonen, E. T. and Francisco, J. S.: HOSO&lt;sub&gt;2&lt;/sub&gt;-H&lt;sub&gt;2&lt;/sub&gt;O Radical Complex and Its Possible Effects on the Production of Sulfuric Acid in the Atmosphere, J. Phys. Chem. A, 107, 1216â€“1221, 2003. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple"> Ahlrichs, R., BÃ¤r, M., HÃ¤ser, M., Horn, H., and KÃ¶lmel, C.: Electronic structure calculations on workstation computers: The program system Turbomole, Chem. Phys. Lett., 162, 165â€“169, 1989. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple"> Alongi, K. S., Dibble, T. S., Shields, G. C., and Kirschner, K. N.: Exploration of the Potential Energy Surfaces, Prediction of Atmospheric Concentrations, and Prediction of Vibrational Spectra for the HO&lt;sub&gt;2&lt;/sub&gt;\ldots(H&lt;sub&gt;2&lt;/sub&gt;O)$_n$ (n=1â€“2) Hydrogen Bonded Complexes, J. Phys. Chem. A, 110, 3686â€“3691, 2006. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple"> Andersson, M. P. and Uvdal, P.: New Scale Factors for Harmonic Vibrational Frequencies Using the B3LYP Density Functional Method with the Triple-Z Basis Set 6-311+G(d,p), J. Phys. Chem. A, 109, 2937â€“2941, 2005. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple"> Atkinson, R., Baulch, D. L., Cox, R. A., Hampson, R. F., Kerr, J. A., Rossi, M. J., and Troe, J. J.: Evaluated Kinetic, Photochemical and Heterogeneous Data for Atmospheric Chemistry: Supplement V. IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry, Phys. Chem. Ref. Data, 26, 521â€“1011, 1997. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple"> Baboul, A. G., Curtiss, L. A., Redfern, P. C., and Raghavachari, K.: Gaussian-3 theory using density functional geometries and zero-point energies, J. Chem. Phys., 110, 7650â€“7658, 1999. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple"> Ball, S. M., Hanson, D. R., Eisele, F. L., and McMurry, P. H.: Laboratory studies of particle nucleation: Initial results for H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;, H&lt;sub&gt;2&lt;/sub&gt;O, and NH&lt;sub&gt;3&lt;/sub&gt; vapors, J. Geophys. Res. D, 104, 23709â€“23718, 1999. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple"> Becke, A. D.: Density-functional thermochemistry. III. The role of exact exchange, J. Chem. Phys., 98, 5648â€“5652, 1993. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple"> Benson, D. R., Young, L.-H., Kameel, F. R., and Lee, S.-H.: Laboratory-measured nucleation rates of sulfuric acid and water: binary homogeneous nucleation from the SO&lt;sub&gt;2&lt;/sub&gt; + OH reaction, Geophys. Res. Lett., 35, L11801, doi:10.1029/2008GL033387, 2008. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple"> Benson, S. W.: Thermochemistry and kinetics of sulphur-containing molecules and radicals, Chem. Rev., 78, 23â€“35, 1978. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple"> Berndt, T., BÃ¶ge, O., Stratmann, F., Heintzenberg, J., and Kulmala, M.: Rapid formation of sulfuric acid particles at near-atmospheric conditions, Science, 307, 698â€“700, 2005. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple"> Berndt, T., BÃ¶ge, O., and Stratmann, F.: Formation of atmospheric H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O particles in the absence of organics: A laboratory study, Geophys. Res. Lett., 33, L15817, doi:10.1029/2006GL026660, 2006. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple"> Berndt, T., BÃ¶ge, O., and Stratmann, F.: Conference Abstract: Atmospheric H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O Particle Formation: Mechanistic Investigations. 17th International Conference on Nucleation and Atmospheric Aerosols (ICNAA), Galway, Ireland, 69â€“72, 2007. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple"> Berndt, T., Stratmann, F., BrÃ¤sel, S., Heintzenberg, J., Laaksonen, A., and Kulmala, M.: SO&lt;sub&gt;2&lt;/sub&gt; oxidation products other than H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; as a trigger of new particle formation. Part~1: Laboratory investigations, Atmos. Chem. Phys., 8, 6365â€“6374, 2008. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple"> Burkholder, J. B., Baynar, T., Ravishankara, A. R., and Lovejoy, E. R.: Particle nucleation following the O&lt;sub&gt;3&lt;/sub&gt; and OH initiated oxidation of Î±-pinene and Î²-pinene between 278 and 320 K, J. Geophys. Res. 112, D10216, doi:10.1029/2006JD007783, 2007. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple"> Curtiss, L. A., Raghavachari, K., Trucks, G. W., and Pople, J. A.: Gaussian-2 theory for molecular energies of first- and second-row compounds, J. Chem. Phys., 94, 7221â€“7230, 1991. </mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple"> Das, T. N.: Reactivity and Role of SO$_5^-$ Radical in Aqueous Medium Chain Oxidation of Sulfite to Sulfate and Atmospheric Sulfuric Acid Generation, J. Phys. Chem. A., 105, 9142â€“9155, 2001. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple"> Davis, D., Ravishankara, A., and Fischer, S.: SO&lt;sub&gt;2&lt;/sub&gt; Oxidation Via the Hydroxyl Radical: Atmospheric Fate of HSO&lt;sub&gt;x&lt;/sub&gt; Radicals, Geophys. Res. Lett., 6, 113â€“116, 1979. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple"> Deegan, M. J. O. and Knowles, P. J.: Perturbative corrections to account for triple excitations in closed and open shell coupled cluster theories, Chem. Phys. Lett., 227, 321â€“326, 1994. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple"> Dermota, T. E., Hydutsky, D. P., Bianco, N. J., and Castleman, A. W. Jr: Ultrafast Dynamics of the SO&lt;sub&gt;2&lt;/sub&gt;(H2O)$_n$ Cluster System, J. Phys. Chem. A, 109, 8254â€“8258, 2005. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple"> Du, S., Francisco, J. S., Schenter, G. K., Iordanov, T. D., Garrett, B., Dupuis, M., and Li, J.: The OH radical-H&lt;sub&gt;2&lt;/sub&gt;O molecular interaction potential, J. Chem. Phys., 124, 224318, doi:10.1063/1.2200701, 2006. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple"> Dunning Jr., T. H., Peterson, K. A., and Wilson, A. K.: Gaussian basis sets for use in correlated molecular calculations. X. The atoms aluminum through argon revisited, J. Chem. Phys., 114, 9244â€“9253, 2001. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple"> Fliegl, H., GlÃ¶ÃŸ, A., Welz, O., Olzmann, M., and Klopper, W.: Accurate computational determination of the binding energy of the SO&lt;sub&gt;3&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt;O complex, J. Chem. Phys., 125, 054312, doi:10.1063/1.2234372, 2006. </mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple"> Frisch, M. J., Trucks, G. W., Schlegel, H. B., Scuseria, G. E., Robb, M. A., Cheeseman, J. R., Montgomery Jr., J. A., Vreven, T., Kudin, K. N., Burant, J. C., Millam, J. M., Iyengar, S. S., Tomasi, J., Barone, V., Mennucci, B., Cossi, M., Scalmani, G., Rega, N., Petersson, G. A., Nakatsuji, H., Hada, M., Ehara, M., Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Klene, M., Li, X., Knox, J. E., Hratchian, H. P., Cross, J. B., Bakken, V., Adamo, C., Jaramillo, J., Gomperts, R., Stratmann, R. E., Yazyev, O., Austin, A. J., Cammi, R., Pomelli, C., Ochterski, J. W., Ayala, P. Y., Morokuma, K., Voth, G. A., Salvador, P., Dannenberg, J. J., Zakrzewski, V. G., Dapprich, S., Daniels, A. D., Strain, M. C., Farkas, O., Malick, D. K., Rabuck, A. D., Raghavachari, K., Foresman, J. B., Ortiz, J. V., Cui, Q., Baboul, A. G., Clifford, S., Cioslowski, J., Stefanov, B. B., Liu, G., Liashenko, A., Piskorz, P., Komaromi, I., Martin, R. L., Fox, D. J., Keith, T., Al-Laham, M. A., Peng, C. Y., Nanayakkara, A., Challacombe, M., Gill, P. M. W., Johnson, B., Chen, W., Wong, M. W., Gonzalez, C., and Pople, J. A.: Gaussian 03, Revision C.02, Gaussian, Inc., Wallingford CT, USA, 2004. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple"> Gleason, J. F., Sinha, A., and Howard, C. J.: Kinetics of the gas-phase reaction HOSO&lt;sub&gt;2&lt;/sub&gt;+O$_2 \to$HO&lt;sub&gt;2&lt;/sub&gt;+SO&lt;sub&gt;3&lt;/sub&gt;, J. Phys. Chem., 91, 719â€“724, 1987. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple"> Gleason, J. F. and Howard, C. J.: Temperature dependence of the gas-phase reaction bisulfite radical + oxygen $\to $ hydroperoxo + sulfur trioxide, J. Phys. Chem. 92, 3414â€“3417, 1988. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple"> Kanno, N., Tonokura, K., and Koshi, M.: Equilibrium constant of the HO&lt;sub&gt;2&lt;/sub&gt;-H&lt;sub&gt;2&lt;/sub&gt;O complex formation and kinetics of HO&lt;sub&gt;2&lt;/sub&gt; + HO&lt;sub&gt;2&lt;/sub&gt;-H&lt;sub&gt;2&lt;/sub&gt;O: Implications for tropospheric chemistry, J. Geophys. Res., 111, D20312, doi:10.1029/2005JD006805, 2006. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple"> Klopper, W., Tew, D. P., GonzÃ¡lez-Garcia, N., and Olzmann, M.: Heat of formation of the HOSO&lt;sub&gt;2&lt;/sub&gt; radical from accurate quantum chemical calculations, J. Chem. Phys., 129, 114308, doi:10.1063/1.2973637, 2008. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple"> Knowles, P. J., Hampel, C., and Werner, H.-J.: Coupled cluster theory for high spin, open shell reference wave functions, J. Chem. Phys., 99, 5219â€“5227, 1993; erratum, J. Chem. Phys., 112, 3106, 2000. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple"> Kulmala, M.: How Particles Nucleate and Grow, Science, 302, 1000â€“1001, 2003. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple"> Kulmala, M., VehkamÃ¤ki, H., PetÃ¤jÃ¤, T., Dal Maso, M., Lauri, A., Kerminen, V.-M., Birmili, W., and McMurry, P. H.: Formation and growth rates of ultrafine atmospheric particles: a review of observations, J. Aerosol Sci., 35, 143â€“176, 2004. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple"> Kulmala, M., Lehtinen, K. E. J., and Laaksonen, A.: Cluster activation theory as an explanation of the linear dependence between formation rate of 3 nm particles and sulphuric acid concentration, Atmos. Chem. Phys., 6, 787â€“793, 2006. </mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple"> Laaksonen, A., Kulmala, M., Berndt, T., Stratmann, F., Mikkonen, S., Ruuskanen, A., Lehtinen, K. E. J., Dal Maso, M., Aalto, P., PetÃ¤jÃ¤, T., Riipinen, I., Sihto, S.-L., Janson, R., Arnold, F., Hanke, M., Ãœcker, J., Umann, B., Sellegri, K., O&apos;Dowd, C. D., and Viisanen, Y.: SO&lt;sub&gt;2&lt;/sub&gt; oxidation products other than H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; as a trigger of new particle formation. Part~2: Comparison of ambient and laboratory measurements, and atmospheric implications, Atmos. Chem. Phys., 8, 7255â€“7264, 2008. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple"> Larson, L. J., Kuno, M., and Tao, F.-M.: Hydrolysis of sulfur trioxide to form sulfuric acid in small water clusters, J. Chem. Phys., 112, 8830â€“8838, 2000. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple"> Lee, C., Yang, W., and Parr, R. G.: Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density, Phys. Rev. B, 37, 785â€“789, 1988. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple"> Li, W.-K. and McKee, M. L.: Theoretical Study of OH and H&lt;sub&gt;2&lt;/sub&gt;O Addition to SO&lt;sub&gt;2&lt;/sub&gt;, J. Phys. Chem. A, 101, 9778â€“9782, 1997. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple"> Lovejoy, E. R. and Hanson, D. R,: Kinetics and Products of the Reaction SO&lt;sub&gt;3&lt;/sub&gt; + NH&lt;sub&gt;3&lt;/sub&gt; + N&lt;sub&gt;2&lt;/sub&gt;, J. Phys. Chem., 100, 4459â€“4465, 1996. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple"> Majumdar, D., Kim, G.-S., Kim, J., Oh, K. S., Lee, J. Y., Kim, K. S., Choi, W. Y., Lee, S.-H., Kang M.-H., and Mhin, B. J.: Ab initio investigations of the HOSO$_2 $+O$_2\to$SO$_3 $+HO&lt;sub&gt;2&lt;/sub&gt; reaction, J. Chem. Phys., 122, 723â€“730, 2000. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple"> Nagase S., Hashimoto, S., and Akimoto, H.: HOSO&lt;sub&gt;2&lt;/sub&gt;, and HOSO&lt;sub&gt;4&lt;/sub&gt;, Radicals Studied by ab Initio Calculation and Matrix Isolation Technique, J. Phys. Chem., 92, 641â€“644, 1988. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple"> Portmann, S.: MOLEKEL, Version 4.3.win32. Swiss Center for Scientific Computing (CSCS)/ETHZ, Switzerland, 2002. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple"> Riipinen, I., Sihto, S.-L., Kulmala, M., Arnold, F., Dal Maso, M., Birmili, W., Saarnio, K., TeinilÃ¤, K., Kerminen, V.-M., Laaksonen, A., and Lehtinen, K. E. J.: Connections between atmospheric sulphuric acid and new particle formation during QUEST IIIâ€“IV campaigns in Heidelberg and Hyytiälä, Atmos. Chem. Phys., 7, 1899â€“1914, 2007. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple"> Salonen, M., KurtÃ©n, T., VehkamÃ¤ki, H., Berndt, T., and Kulmala, M.: Computational investigation of the possible role of some intermediate products of SO&lt;sub&gt;2&lt;/sub&gt; oxidation in sulfuric acid â€“ water nucleation, Atmos. Res., Atmos. Res., 91, 47â€“52, 2009. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple"> Solimannejad, M., Azimi, G., and Pejov, L: The HOOâ€“SO&lt;sub&gt;3&lt;/sub&gt; radical complex: ab initio and density-functional study, Chem. Phys. Lett., 391, 201â€“206, 2004. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple"> Stockwell, W. R. and Calvert, J. G.: The mechanism of the HO-SO&lt;sub&gt;2&lt;/sub&gt; reaction, Atmos. Environ., 17, 2231â€“2235, 1983. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple"> Wavefunction, Inc: Spartan &apos; 02 Windows, Wavefunction, Inc., Irvine, CA, USA, www.wavefun.com, 2002. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple"> Wayne, R. P.: Chemistry of atmospheres, 3rd edition, Oxford University Press., Oxford, UK, 2000. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple"> Weber, R. J., McMurry, P. H., Eisele, F. L., and Tanner, D. J.: Measurements of expected nucleation precursor species and 3â€“500-nm diameter particles at Mauna Loa observatory, Hawaii, J. Atmos. Sci., 52, 2242â€“2257, 1995. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple"> Weigend, F. and HÃ¤ser, M.: RI-MP2: first derivatives and global consistency, Theor. Chem. Acc., 97, 331â€“340, 1997. </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple"> Weigend, F., HÃ¤ser, M., Patzelt, H., and Ahlrichs, R.: RI-MP2: Optimized auxiliary basis sets and demonstration of efficiency, Chem. Phys. Lett., 294, 143â€“152, 1998. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple"> Werner, H.-J., Knowles, P. J., Lindh, R., Manby, F. R., SchÃ¼tz, M., Celani, P., Korona, T., Rauhut, G., Amos, R. D., Bernhardsson, A., Berning, A., Cooper, D. L., Deegan, M. J. O. , Dobbyn, A. J., Eckert, F., Hampel, C., Hetzer, G., Lloyd, A. W., McNicholas, S. J., Meyer, W., Mura, M. E., Nicklass, A., Palmieri, P., Pitzer, R., Schumann, U., Stoll, H., Stone, A. J., Tarroni, R., and Thorsteinsson, T.: MOLPRO, version 2006.1, a package of ab initio programs, see http://www.molpro.net, 2006. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple"> Young, L. H., Benson, D. R., Kameel, F. R., Pierce, J. R., Junninen, H., Kulmala, M., and Lee, S.-H.: Laboratory studies of H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O binary homogeneous nucleation from the SO&lt;sub&gt;2&lt;/sub&gt;+OH reaction: evaluation of the experimental setup and preliminary results, Atmos. Chem. Phys., 8, 4997â€“5016, 2008. </mixed-citation>
</ref>
</ref-list>
</back>
</article>