title: Ultraviolet light-induced water-droplet formation from wet ambient air.
abstract: We report the formation of water droplets by irradiating wet ambient air with deep UV light. The light sources were either a continuous low-pressure mercury lamp or pulsed ArF laser, which both emit light shorter than 200 nm. Water droplets were produced in reaction vessels under different temperature, relative humidity, and moisture-supply conditions. The particles grew as large as about 0.2 mm. The suggested mechanism is discussed with the photo-dissociations of oxygen and successively formed ozone, and further dark reactions giving hydrogen peroxide as a seeding nucleus. Observed concentrations of intermediates were well explained by simulating the proposed chemical reactions. A possible application to artificial rain is briefly described.
authors.affiliation: Toyota Physical and Chemical Research Institute, Aichi, Japan .
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yoshihara
authors.affiliation: Toyota Central R&D Laboratory, Aichi, Japan .
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Takatori
authors.affiliation: Department of Applied Chemistry, Tokyo Metropolitan University, Tokyo, Japan .
authors.forename: Koji
authors.initials: K
authors.lastname: Miyazaki
authors.affiliation: Department of Applied Chemistry, Tokyo Metropolitan University, Tokyo, Japan .
authors.forename: Yoshizumi
authors.initials: Y
authors.lastname: Kajii
keywords: hydrogen peroxide; nucleation of water; photochemical seeding; ultraviolet light; water droplet formation; wet air