Why formation rate of 3 nm particles depends linearly on sulphuric acid concentration?
1University of Helsinki, Department of Physical Sciences, P.O. Box 64, FIN-00014 Helsinki, Finland
2Finnish Meteorological Institute and University of Kuopio, Department of Applied Physics, P.O. Box 1627, FIN-70211 Kuopio, Finland
3University of Kuopio, Department of Applied Physics, P.O. Box 1627, FIN-70211 Kuopio, Finland
Abstract. According to atmospheric observations new particle formation seems to be a function of sulphuric acid concentration to the power from one to two. The nucleation theorem then predicts that the critical cluster contains one to two sulphuric acid molecules. However, existing nucleation theories predicts that the power is more (or equal) than 2. Here we present an activation theory, which can explain the observed slope. In cluster activation the clusters containing one sulphuric acid molecule will activate for further growth due to heterogeneous nucleation, heterogeneous chemical reactions including polymerization or activation of soluble clusters. In the activation process organic vapours are typically needed as condensing agents.