Homogeneous Nucleation of Ice in Transiently-Heated, Supercooled Liquid Water Films.

We have investigated the nucleation and growth of crystalline ice in 0.24 μm thick, supercooled water films adsorbed on Pt(111). The films were transiently heated with ∼10 ns infrared laser pulses, which produced typical heating and cooling rates of ∼109-1010 K/s. The crystallization of these water films was monitored with infrared spectroscopy. The experimental conditions were chosen to suppress ice nucleation at both the water/metal and water/vacuum interfaces. Furthermore, internal pressure increases due to curvature effects are precluded in these flat films. Therefore, the experiments were sensitive to the homogeneous ice nucleation rate from ∼210 to 225 K. The experiments show that Jmax, the maximum for the homogeneous ice nucleation rate, J(T), needs to be ≥1026 m-3 s-1 and is likely to be ∼1029±2 m-3 s-1. We argue that such large nucleation rates are consistent with experiments on hyperquenched glassy water, which typically have crystalline fractions of ∼1% or more.