Direct molecular-level characterization of different heterogeneous freezing modes on mica – Part 1

Abstract

Abstract. The mechanisms behind heterogeneous ice nucleation are of fundamental importance to the prediction of the occurrence and properties of many cloud types, which influence climate and precipitation. Aerosol particles act as cloud condensation and freezing nuclei. The surface-water interaction of an ice nucleation particle plays a major, not well explored, role in its ice nucleation ability. This paper presents a real-time molecular-level comparison of different freezing modes on the surface of an atmospherically relevant mineral surface (mica) under varying supersaturation conditions using second-harmonic generation spectroscopy. Two sub-deposition nucleation modes were identified (one-and two-stage freezing). The nonlinear signal at the water-mica interface was found to drop following the formation of a thin film on the surface regardless of (1) the formed phase (liquid or ice) and (2) the freezing path (one or two step), indicating similar molecular structuring. The results also revealed a transient phase of ice at water-mica interfaces during freezing, which has a lifetime of around 1 min. Such information will have a significant impact on climate change, weather modification, and the tracing of water in hydrosphere studies.

Cloud history can change water–ice–surface interactions of oxide mineral aerosols: a case study on silica

“…3). It has been shown in different studies on the water-mineral oxide interface that a higher degree of ordering of liquid water molecules next to the surface is an indication of higher heterogeneous freezing efficiency (Abdelmonem, 2017;Abdelmonem et al, 2017Abdelmonem et al, , 2015Anim-Danso et al, 2013Yang et al, 2011). In the present work, it was our intention to impose a constant cooling rate to qualitatively follow the freezing efficiency and interfacial water structural changes under identical conditions.…”

“…The SHG experiments were conducted using a 1 kHz femtosecond (fs) laser system (Solstice, Spectra-Physics, 800 nm, 3.5 mJ, ∼ 80 fs) with a beam diameter of ∼ 2 mm at the interface. More details on the optical setup and the measuring cell can be found elsewhere (Abdelmonem et al, 2015Abdelmonem, 2017). The fundamental beam was incident on the interface (Fig.…”

“…The silica prism was attached to the cold stage, and the surface of interest was exposed to the sample solution filled in a Teflon cell during the experiments. More details and drawings of the environmental chamber can be found elsewhere (Abdelmonem, 2017).…”

“…Although this study was not aimed at discussing the transient freezing peak, the obtained data force us to reconsider this recently observed ambiguous phenomenon. The transient peak upon freezing was reported at pH 9.8 for the aqueoussolution-mica interface using SFG (sum-frequency generation) spectroscopy (Anim-Danso et al, 2016), for a neutral water-silica interface using SFG spectroscopy (Lovering et al, 2017), for a neutral water-mica and water-sapphire interface using SHG spectroscopy (Abdelmonem, 2017), and for a pH 9 aqueous-solution-sapphire interface using SFG spectroscopy (Abdelmonem et al, 2018). Anim-Danso et al (2016) supposed that the transient signal is due to progressive events occurring near the surface during the phase transition, without specifying a potential process.…”

Cloud history changes water–ice–surface interactions of oxide mineral aerosols (e.g. Silica)

“…Hoose and Möhler have reported the wide scatter in IN efficiencies of same aerosol particles collected from different sources and examined in 25 different laboratories (Hoose and Mohler, 2012). There have been previous efforts to understand the influence of surface properties on water freezing such as the effects of charge, e.g., on ice formation by aluminum oxide (Anim-Danso et al, 2016;Abdelmonem et al, 2017) or morphology, e.g., for Feldspar (Kiselev et al, 2017) and Kaolinite (Wang et al, 2016).…”