title: Phase transfer and freezing processes investigated on acoustically levitated aqueous droplets.
abstract: An acoustic trap was designed and constructed to investigate, on a microscale, physicochemical processes relevant to the troposphere, mainly focusing on the temperature range below 0 degrees C. Droplets ranging from 0.5 nL to 4 microliter (0.1 to 2 mm in diameter) were introduced into the cooled reaction chamber by means of a piezo-driven micro pump with a reproducibility better than 5%. Up-take of H2O2 from the gas phase by the levitated droplet was measured and calibrated by in-situ chemiluminescence. Freezing of stably positioned droplets was observed and documented by means of a microscope and a video camera; this demonstrated the usefulness of the technique for simulation and investigation of cloud processes. Ex-situ microanalysis of sub-microliter droplets by use of a fiber optic luminometer was also shown to be a suitable means of investigating relevant physicochemical processes on a micro scale.
authors.affiliation: Institut für Spektrochemie und Angewandte Spektroskopie (ISAS), Dortmund, Germany. jacob@isas-dortmund.de
authors.forename: P
authors.initials: P
authors.lastname: Jacob
authors.forename: A
authors.initials: A
authors.lastname: Stockhaus
authors.forename: R
authors.initials: R
authors.lastname: Hergenröder
authors.forename: D
authors.initials: D
authors.lastname: Klockow