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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 7203-7216, 2015
https://doi.org/10.5194/acp-15-7203-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
01 Jul 2015
Experimental investigation of ion–ion recombination under atmospheric conditions
A. Franchin1, S. Ehrhart2,10, J. Leppä3,4, T. Nieminen1,5, S. Gagné6,7, S. Schobesberger1, D. Wimmer1, J. Duplissy5, F. Riccobono8, E. M. Dunne9, L. Rondo10, A. Downard4, F. Bianchi8,11, A. Kupc12, G. Tsagkogeorgas13, K. Lehtipalo1, H. E. Manninen1, J. Almeida2, A. Amorim14, P. E. Wagner12, A. Hansel15, J. Kirkby2,10, A. Kürten10, N. M. Donahue16, V. Makhmutov17, S. Mathot2, A. Metzger15, T. Petäjä1, R. Schnitzhofer15, M. Sipilä1, Y. Stozhkov17, A. Tomé14, V.-M. Kerminen1,3, K. Carslaw18, J. Curtius10, U. Baltensperger8, and M. Kulmala1 1Department of Physics, P.O. Box 64, 00014 University of Helsinki, Helsinki, Finland
2CERN, 1211 Geneva, Switzerland
3Finnish Meteorological Institute, Atmospheric Composition Research, P.O. Box 503, 00101 Helsinki, Finland
4California Institute of Technology, Department of Chemical Engineering, 1200 E. California Blvd., Mail Code 101-20, Pasadena, CA 91125, US
5Helsinki Institute of Physics, Helsinki, Finland
6Department of Physics and Atmospheric Science, Dalhousie University, Halifax, B3H 3J5, Canada
7Environment Canada, Downsview, Toronto, M3H 5T4, Canada
8Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
9Finnish Meteorological Institute, Kuopio Unit, P.O. Box 1627, 70211 Kuopio, Finland
10Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany
11Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
12University of Vienna, Universitätsring 1, 1010 Vienna, Austria
13Leibniz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany
14CENTRA-SIM, F.C.U. Lisboa and U. Beira Interior, Portugal
15Ionicon Analytik GmbH and University of Innsbruck, Institute for Ion and Applied Physics, 6020 Innsbruck, Austria
16Carnegie Mellon University, Center for Atmospheric Particle Studies, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
17Lebedev Physical Institute, Leninsky Prospect 53, 119991 Moscow, Russia
18School of Earth and Environment, University of Leeds, LS2 9JT, Leeds, UK
Abstract. We present the results of laboratory measurements of the ion–ion recombination coefficient at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. The experiments were carried out using the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at CERN, the walls of which are made of conductive material, making it possible to measure small ions. We produced ions in the chamber using a 3.5 GeV c−1 beam of positively charged pions (π+) generated by the CERN Proton Synchrotron (PS). When the PS was switched off, galactic cosmic rays were the only ionization source in the chamber. The range of the ion production rate varied from 2 to 100 cm−3 s−1, covering the typical range of ionization throughout the troposphere. The temperature ranged from −55 to 20 °C, the relative humidity (RH) from 0 to 70 %, the SO2 concentration from 0 to 40 ppb, and the ozone concentration from 200 to 700 ppb. The best agreement of the retrieved ion–ion recombination coefficient with the commonly used literature value of 1.6 × 10−6 cm3 s−1 was found at a temperature of 5 °C and a RH of 40 % (1.5 ± 0.6) × 10−6 cm3 s−1. At 20 °C and 40 % RH, the retrieved ion–ion recombination coefficient was instead (2.3 ± 0.7) × 10−6 cm3 s−1. We observed no dependency of the ion–ion recombination coefficient on ozone concentration and a weak variation with sulfur dioxide concentration. However, we observed a more than fourfold increase in the ion–ion recombination coefficient with decreasing temperature. We compared our results with three different models and found an overall agreement for temperatures above 0 °C, but a disagreement at lower temperatures. We observed a strong increase in the recombination coefficient for decreasing relative humidities, which has not been reported previously.

Citation: Franchin, A., Ehrhart, S., Leppä, J., Nieminen, T., Gagné, S., Schobesberger, S., Wimmer, D., Duplissy, J., Riccobono, F., Dunne, E. M., Rondo, L., Downard, A., Bianchi, F., Kupc, A., Tsagkogeorgas, G., Lehtipalo, K., Manninen, H. E., Almeida, J., Amorim, A., Wagner, P. E., Hansel, A., Kirkby, J., Kürten, A., Donahue, N. M., Makhmutov, V., Mathot, S., Metzger, A., Petäjä, T., Schnitzhofer, R., Sipilä, M., Stozhkov, Y., Tomé, A., Kerminen, V.-M., Carslaw, K., Curtius, J., Baltensperger, U., and Kulmala, M.: Experimental investigation of ion–ion recombination under atmospheric conditions, Atmos. Chem. Phys., 15, 7203-7216, https://doi.org/10.5194/acp-15-7203-2015, 2015.
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The ion-ion recombination coefficient was measured at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. The experiments were carried out using the CLOUD chamber at CERN. We observed a strong dependency on temperature and on relative humidity, which has not been reported previously. No dependency of the ion-ion recombination coefficient on ozone concentration was observed and a weak variation with sulfur dioxide concentration was also observed.
The ion-ion recombination coefficient was measured at different temperatures, relative...
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