Dynamic light scattering at a growing crystal interface: Ice-water system

We have examined quasielastic light scattering off the crystal-melt interface of growing ice crystals using photon correlation spectroscopy. The intensity autocorrelation spectra exhibit two exponential decay rates with vastly different time constants. The fast decay is found only during growth and is similar to that observed by Bilgram and his co-workers. We have found several new features associated with the slow-decay component: (1) nonzero intercept of the decay constant Γ versus the square of the scattering vector $q^2$ during growth; (2) a liftoff layer that depends on the type of gaseous impurity; and (3) a direct relationship between the effective hydrodynamic radius of the slow component and the degree of its size polydispersity. These provide new evidence to support Cummins’s hypothesis that this component of the spectrum is caused by the segregation and precipitation of tiny gas bubbles at the crystal’s surface.