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Quasi-liquid layers on ice crystal surfacesSazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS, 109, 1052-1055.Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers, CGD, 15, 3339-3344.Quasi-liquid layers: why do we care?Because theyre really cool.Introduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyIntroduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyPenetrates surfacePenetrates surfacePenetrates surfaceIntroduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyPenetrates surfacePenetrates surfacePenetrates surfaceIntroduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyHigh vacuumHigh vacuumIntroduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyHigh vacuumHigh vacuumIntroduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyEllipsometryGrazing-incidence x-ray diffractionConfocal laser scanning microscopyNuclear magnetic resonanceInterference microscopyInterferometryIntroduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyEllipsometryGrazing-incidence x-ray diffractionConfocal laser scanning microscopyNuclear magnetic resonanceInterference microscopyInterferometryIce destroys AFM tipsDifficult and questionable precisionPoor resolutionIce is mostly transparent Introduction: measurements of surface propertiesDifferent ways to measure surface propertiesX-ray diffractionNeutron backscatteringElectron scatteringLow-energy electron scatteringInfrared spectroscopyVoltammetryTunneling electron microscopyAtomic force microscopyEllipsometryGrazing-incidence x-ray diffractionConfocal laser scanning microscopyNuclear magnetic resonanceInterference microscopyInterferometryAmbiguous resultsnice nwaterVery difficult interpretationIntroduction: so whos tried this?Faraday (1840s) (1860, PRSL)Several clever experiments showing that water particles on ice can briefly turn to liquid before freezing again (experimental)Thomson and Lord Kelvin (1850-1870s)Faraday must be daft. The surface of ice is just melting because the extra pressure lowers the melting pointFletcher (1962, Phil. Mag.)First theoretical treatment of QLL, used thermodynamics and kinetics to show QLLs are possible and probable (theoretical)Jellinek (1967, JCIS)First literature review in the field of water ice QLLKuroda and Lacmann (1982, JCG)QLLs modulate vapor depositional growth at high temperatures with different temperature dependence for the two different facets (theoretical)Elbaum, et al. (1993, JCG)Optical measurements (ellipsometry and interference microscopy) detected possible QLLIntroduction: so whos tried this?Knight (1996, JGR)QLLs dont make physical sense, theyre not thermodynamically possible, and even as a conceptual model theyre useless (comment)Baker and Dash (1996, JGR)Charlie Knight is applying macroscopic thermodynamics to a nanoscale system (reply)Nelson and Knight (1998, JAS)There is little doubt that the ice surface is rather badly disturbed at temperatures not far below zero but Kuroda and Lacmann are wrong about QLL. (theoretical)Ewing (2004, JPCB)QLL is difficult to measure, but IR can tell us some things. QLL kind of appears to be a different phase (experimental review)Nunes, et al. (2007, Solid State NMR)No evidence of QLL, but proving NMR as a possible technique (theoretical)Sazaki, et al. (2012, PNAS)First unambiguous observation of two types of QLL on basal facetsAsakawa, et al. (2015, CGD)First unambiguous observation of two types of QLL on prism facets0.37-nm vertical resolutionCreates images by scanning the laser across the crystalAllows video imaging of individual step growth

(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Fig S2 (Asakawa, 2015)

Fig S2 (Sazaki, 2012)Laser confocal microscopy-differential interference microscopy (LCM-DIM)Round droplet-like features formed at -1.5 to -0.4C: -QLLsInterference measurements give heights of approximately 0.5 m for a width of 50 mIndicates high wettability of ice surface by QLL(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Round liquid-like droplets

-0.4C-0.3C-0.6C-0.3CFigure 1.each band is 317 nmCoalescence of -QLLs shows they cannot be solidThey appear to serve as step sources (Sazaki, et al. say they nucleate steps)(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Coalescence of -QLLstemperature: -0.3Cduration: 38 seconds

Movie S1Thin layers form at -1.0 to -0.2C: -QLLsClearly thicker than steps, but too thin for interferometry: thickness < 100 nmDroplets and thin layers (not shown here) eventually coalesce(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Formation of thin layerstemperature: -0.1Cduration: 88 seconds

Movie S2Adjusting image settings shows steps underneath the -QLLEither -QLL deforms over steps, or QLL refractive index is different than iceThin layers cannot be solid ice(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Seeing through -QLLstemperature: -0.1Cduration: 163.5 seconds

Movie S3Temperature decreased -0.5 to -1.0C-QLL decomposed and changed into -QLLs and many bunched stepsShows reversibility and phase stability of the transitions between - and -QLLs-QLLs are more stable than -QLLs in the measured case(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Refreezing of QLLstemperature: -0.5 to -1.0Cduration: 163.5 seconds

Movie S4According to classical thermodynamics:-QLLs are more thermodynamically favorable: high wettability means low interaction energy with ice-QLLs are more stable: lower appearance temperature-QLLs always appear after -QLLs(Sazaki, et al., 2012: Quasi-liquid layers on ice crystal surfaces are made up of two different phases, PNAS.)Other notes from Sazaki, et al.Figure S1.

Roughening transition on prism/high-index facetsScrew dislocation growth at -4.4C (A)Distances between steps decrease at -3.0C (B; 42.1 seconds later)Surface becoming rounded (C; 501.0 seconds later)Almost no reflection off surface (D; 1081.0 seconds later)(Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers. CGD.)Figure 1.

QLLs on prism/high-index facetsPrism facet experiencing a roughening transition/becoming roundedLiquid-like droplets appear (little lumps on face)(Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers. CGD.)Figure 2.

Liquid-like coalescing on a a prism/high-index facetTwo liquid-like droplets coalescing to form one droplet(Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers. CGD.)

Figure 3.Movie S1.-0.5C

(Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers. CGD.)

Figure 4.Thin liquid-like layers on a prism/high-index facetThin layers coalescing to cover the surfaceLiquid-like layer appearing underneath liquid-like dropLiquid-like drops apparently condensing in to a growing liquid-like layer(Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers. CGD.)

Figure 5.Thin liquid-like layers coalescing again

(Asakawa, et al., 2015: Prism and Other High-Index Faces of Ice Crystals Exhibit Two Types of Quasi-Liquid Layers. CGD.)Figure 6.Summary of overall findings

-QLLs are less stable (probably)-QLLs always form firstBoth are difficult to observe on prism/high-index faces