title: Physical Chemistry of the Freezing Process of Atmospheric Aqueous Drops.
abstract: In supercooled aqueous solutions, ice nucleation is the initial stage of the freezing process. In this paper, we present experimental results that indicate that during the freezing of aqueous solutions, freeze-induced phase separation (FIPS) into pure ice and a freeze-concentrated solution (FCS) takes place. Our observations involve the use of an optical cryo-microscope (OC-M) to record images and movies. The results visually indicate for the first time that there are two freezing processes for (NH4)3H(SO4)2/H2O solutions: (i) contact freezing, as is the case for pure water drops, and (ii) the Wegener-Bergeron-Findeisen process, which is the growth of frozen drops (ice) at the expense of liquid ones. We also present OC-M images of frozen micrometer-scaled H2SO4/H2O drops that support our previous finding that freezing of these solutions generates mixed-phase particles, namely an ice core coated with a FCS. These results are relevant for atmospheric as well as for pharmaceutical sciences.
authors.affiliation: Laboratory of Polymer Chemistry, Department of Chemistry, University of Helsinki , P.O. Box 55, FI-00014 Helsinki, Finland.|Department of Physics, University of Helsinki , P.O. Box 48, FI-00014 Helsinki, Finland.
authors.forename: Anatoli
authors.identifier: http://orcid.org/0000-0001-7339-6673
authors.initials: A
authors.lastname: Bogdan
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093-0356, United States.
authors.forename: Mario J
authors.initials: MJ
authors.lastname: Molina