title: Single freezing and triple melting of micrometre-scaled (NH4)2SO4/H2O droplets.
abstract: Atmospheric aerosol droplets containing NH(4)(+) and SO(4)(2-) ions are precursors of cirrus ice clouds. However, the low-temperature phase transformation of such droplets is not understood yet. Here we show for the first time that micrometre-scaled (NH(4))(2)SO(4)/H(2)O droplets produce one freezing event but three melting events which are the melting of (i) pure ice, (ii) eutectic ice/(NH(4))(2)SO(4), and (iii) eutectic ice/(NH(4))(3)H(SO(4))(2). We also find that the melting of ice/(NH(4))(3)H(SO(4))(2) consists of two eutectic melting events, presumably ice/letovicite-II and ice/letovicite-III.
authors.affiliation: Institute of Physical Chemistry, University of Innsbruck, Innsbruck, Austria. anatoli.bogdan@uibk.ac.at
authors.forename: Anatoli
authors.initials: A
authors.lastname: Bogdan
authors.forename: Mario J
authors.initials: MJ
authors.lastname: Molina
authors.forename: Heikki
authors.initials: H
authors.lastname: Tenhu
authors.forename: Thomas
authors.initials: T
authors.lastname: Loerting