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 J_max, the maximum for the homogeneous ice nucleation rate, J(T), needs to be ≥10²⁶ m^-3 s^-1 and is likely to be ∼10^29±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.