DYNAMIC LIGHT-SCATTERING AT THE ICE WATER INTERFACE DURING FREEZING

The 488 nm radiation of an argon laser is scattered quasi-elastically at the [0001]-face (basal plane) of a growing ice crystal. The scattering plane is the basal plane. The Rayleigh-linewidth is proportional to the square of the scattering vector. One measures about 2 krad/s at a scattering angle of 90°. The linewidth does not depend on the growth rate. Scattering is only observed once a critical growth rate νcrit = 1,5 μ m{plus 45 degree rule}s has been exceeded. Then the scattering intensity depends linearly on the growth rate in the range between 0,03 μ m{plus 45 degree rule}s and 2,5 μ m{plus 45 degree rule}s. Once the surface is molten scattering vanishes and does not reappear until the growth rate has again exceeded the threshold νcrit. The coherence properties of the scattered light indicate that the thickness of the scattering layer is less than 6 μ m. The observations are interpreted in terms of a fluctuating interface. The decay time of the fluctuations has been calculated. Satisfactory agreement with the observed Rayleigh linewidth is obtained. © 1979.