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Water is unlikely to crystallize homogeneously at temperatures greater than -34 °C. Freezing at higher temperatures is heterogeneous-catalyzed by the presence of a second substance. If that substance is at an air-water interface, then the mode is called contact freezing, and it typically will trigger nucleation at a higher temperature than if the substance were wholly immersed within the liquid. We find that the impact of salt particles initiates freezing in experiments using water droplets at supercoolings of 9 to 16 °C. These results show that contact freezing nuclei need not be effective as immersion mode nuclei. We discuss our results in the context of proposed mechanisms of contact freezing. Finally, we use the time scales for diffusion of heat and of ions and the propagation of a sound wave through the droplet to estimate that contact freezing occurs within 10 ns of impact.

A small push-pull molecule involving a diphenylamine substituted by an oligo-oxyethylene chain is described. The compound exhibits aggregation-induced emission with solvent-dependent emission wavelength. Spin-cast deep-red amorphous films rapidly self-reorganize into colorless crystalline films which exhibit mechanofluorochromism and aggregation-induced second-harmonic generation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The discovery of HArF has generated renewed interest in the chemistry of noble gases, particularly their hydrides. Though many weak complexes of noble gases bound by van der Waals interactions are known, the number of halogenated noble gas compounds, HNgX (Ng = noble gas; X = halogen), where the noble gas atom is chemically bound, is limited. These molecules are metastable, and their specialty is that there is substantial ionic bonding between the noble gas atom and the halogen atom. In this Letter, it is shown using density functional theory and second-order Møller-Plesset perturbation theory that by replacing the halogen atoms by superhalogens (Y), whose electron affinities are much larger than those of halogens, more ionic bonds between Ng and Y can be attained. Moreover, the superhalogen-containing noble gas hydrides, HNgY, are more stable compared to their halogenated counterparts.

A dramatic increase in the surface tension of water with decreasing temperature in the supercooled liquid region has appeared as one of the many anomalies of water. This claimed anomaly characterized by the second inflection point at about +1.5 °C was observed in older surface tension data and was partially supported by some molecular simulations and theoretical considerations. In this study, two independent sets of experimental data for the surface tension of water in the temperature range between +33 and -25 °C are reported. The two data sets are mutually consistent, and they lie on a line smoothly extrapolating from the stable region. No second inflection point and no other anomalies in the course of the surface tension were observed. The new data lies very close to the extrapolated IAPWS correlation for the surface tension of ordinary water, which hence can be recommended for use, e.g., in atmospheric modeling.

A number of laser-induced fluorescence and absorption spectroscopy studies have been conducted using Gaseous Electronics Conference Reference Cells. Laser-induced fluorescence has been used to measure hydrogen atom densities, to measure argon metastable spatial profiles, to determine the sheath electric field, and to infer the electron density and temperature. Absorption spectroscopy, using lamp sources and diode lasers, has been used to measure metastable atom densities in helium and argon discharges and fluorocarbon densities in silicon etching discharges. The experimental techniques and sample results of these investigations are reviewed.