Enhanced Density Fluctuations in SupercooledH2O,D2O, and Ethanol-Water Solutions: Evidence from Small-Angle X-Ray Scattering

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Abstract
The static structure factor S(q) for H2O was measured by x-ray scattering for 0.15Å−1<q<1Å−1 and for 253 K<T<348 K. The low-temperature data show a surprising increase of S(q) with decreasing q, which can be fitted with a Lorentzian whose width corresponds to density fluctuations with a length scale that increases to about 8 Å as T is decreased to 253 K. The anomaly is more pronounced in D2O, while small amounts of the hydrogen-bonding impurity ethanol decrease the anomaly.