Sub-10 nm particle growth by vapor condensation – effects of vapor molecule size and particle thermal speed 1Department of Physics, P.O. Box 64, 00014, University of Helsinki, Finland
2Finnish Meteorological Institute, Kuopio Unit, and University of Kuopio, Department of Physics, P.O. Box 1627, 70211 Kuopio, Finland
Received: 05 Jan 2010 – Published in Atmos. Chem. Phys. Discuss.: 21 Jan 2010 Abstract. The growth of freshly formed nanoparticles has been investigated. A new analytical
expression based on a recently developed exact solution for the condensational growth rate
has been derived. Based on the new growth rate, a new approximate but accurate analytical
expression for growth time has been derived. The expression includes transition regime
effects on growth, molecule size effects on the collision cross section and particle
thermal speed effects on the relative collisional speeds – the last two of which are typically
neglected, but may have significant effects when dealing with the growth of freshly
nucleated particles. To demonstrate the use of the derived expressions, the contribution of
sulphuric acid and organic compounds on sub 3 nm and sub 10 nm particle growth rates has
been studied. For sulphuric acid also the effect of hydration as function of relative
humidity has been taken into account. According to the new expression the sulphuric
acid concentration needed for 1 nm/h growth in sub 3 nm range is ca.
1.5×107 cm−3, which is a factor of 1.5 smaller than values typically used in aerosol
physics based on standard model in kinetic regime.
Revised: 28 May 2010 – Accepted: 01 Jun 2010 – Published: 18 Oct 2010
Citation: Nieminen, T., Lehtinen, K. E. J., and Kulmala, M.: Sub-10 nm particle growth by vapor condensation – effects of vapor molecule size and particle thermal speed, Atmos. Chem. Phys., 10, 9773-9779, doi:10.5194/acp-10-9773-2010, 2010.