Applicability of condensation particle counters to measure atmospheric clusters

1 Department of Physical Sciences, University of Helsinki, Finland 2 Helsinki Institute of Physics, Helsinki, Finland 3 Institute for Atmospheric Physics, J. Gutenberg-University Mainz, Mainz, Germany 4 Max Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany 5 School of Physics & Centre for Climate and Air Pollution Studies, Environmental Change Institute, National University of Ireland, Galway, Ireland * now at: Earth and Sun Systems Laboratory, Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, USA ** now at: Institute for Atmosphere and Environment, J. W. Goethe-University Frankfurt, Frankfurt am Main, Germany *** now at: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA