Properties of the solid–liquid interface layer of growing ice crystals: A Raman and Rayleigh scattering study

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Abstract
The interface layer in front of an ice crystal growing into the melt has been studied simultaneously by Raman and Rayleigh scattering. The Raman spectra of the light scattered from the interface layer material give evidence for intermolecular dynamics which cannot be detected in either bulk phase. The Rayleigh scattering data are in agreement with the data of Böni et al. [Phys. Rev. A 28, 2953 (1983)], who have discovered the interface layer. For the first time it has been possible to measure the thickness of the layer as a function of the growth rate. At high growth rates enhanced Rayleigh scattering originating from the interface layer of a thickness of about 3 μm has been observed. With decreasing growth rate the thickness of the layer increases, reaching up to 200 μm at zero growth rate, and at melting the layer stays back in the water. From the linewidth of the Rayleigh scattered light we deduce a diffusion constant Di≈2×10−8 cm2/s. Raman spectra show that the intermolecular structure in the interface layer is essentially water-like. Compared to water additional intensity has been observed in the polarized Rayleigh wing, indicating a new polarized and unshifted line with a linewidth that corresponds to a relaxation time τ0≈4×10−13 s. It is tentatively assigned to the decay of a symmetric, intermolecular structure occurring in the interface layer. Slight differences found in the O–H stretching band can be interpreted as a small increase of the average number of H bonds per water molecule in the interface layer as compared to bulk water. The O–H stretching band looks as if the water in the interface layer has a temperature which is about 3 deg colder as it actually is.