Henrik Svensmark, Martin B. Enghoff, Jens Olaf Pepke Pedersen. Response of cloud condensation nuclei (>50 nm) to changes in ion-nucleation. Physics Letters A, Volume 377, Issue 37, 8 November 2013, Pages 2343–2347.
In experiments where ultraviolet light produces aerosols from trace amounts of ozone, sulfur dioxide, and water vapor, the relative increase in aerosols produced by ionization by gamma sources is constant from nucleation to diameters larger than 50 nm, appropriate for cloud condensation nuclei. This result contradicts both ion-free control experiments and also theoretical models that predict a decline in the response at larger particle sizes. This unpredicted experimental finding points to a process not included in current theoretical models, possibly an ion-induced formation of sulfuric acid in small clusters.
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