Funada, Shuhei

Hvelplund, Preben

Kobara, Hitomi

Nakai, Youchi

Pedersen, Jens Olaf Pepke

Sasa, Kimikazu

Shigeoka, Tomita

The droplet formation induced by cosmic ray in the terrestrial atmosphere attract certainattention in recent decades because this process could be important to understand thepossible relationship between cosmic ray and climate on the earth. The role of energetic ionsfor the droplet formation would be in both the ion production and oxidation of SO2 in the air.Attractive polarization forces between ions and molecules decrease energy barrier in dropletgrowth. On the other hand, the oxidation of SO2 by radical species in ion irradiation result inthe production of H2SO4, which also decrease energy barrier of the droplet growth in thebinary nucleation process of water and H2SO4.We have performed irradiation of proton beam on the gas mixture of N2/H2O/SO2 andAir/H2O/SO2. The reduction of SO2 concentration by beam irradiation was monitored usingan SO2 meter and the size distributions of generated droplets were measured with adifferential mobility analyzer. We found that the mass yield of generated droplets showedlinear dependence on the amount of SO2 oxidation. This behavior is different from binarynucleation theory of water and H2SO4. The difference might indicates importance ofconsidering the droplet formation to be a kind of cooperative phenomena by ion processesand oxidation of SO2.<br/

Formation of Nanodroplets in N<sub>2</sub>/H<sub>2</sub>O/SO<sub>2</sub> under Irradiation of Fast Proton Beams

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