Response of Cloud Condensation Nuclei (> 50 nm) to changes in ion-nucleation

TL;DR

This study investigates how ionization influences the growth of cloud condensation nuclei larger than 50 nm, revealing unexpected results that challenge existing theoretical models and suggest new formation processes.

Contribution

It provides experimental evidence that ionization can enhance growth of larger aerosols, indicating a missing process in current models of particle growth.

Findings

Ionization increases growth of particles >50 nm

Contradicts existing models predicting decline in larger particle growth

Suggests ion-induced sulphuric acid formation as a new process

Abstract

In experiments where ultraviolet light produces aerosols from trace amounts of ozone, sulphur dioxide, and water vapour, the number of additional small particles produced by ionization by gamma sources all grow up 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 of larger particles due to an insufficiency of condensable gases (which leads to slower growth) and to larger losses by coagulation between the particles. This unpredicted experimental finding points to a process not included in current theoretical models, possibly an ion-induced formation of sulphuric acid in small clusters.