Temperature Dependence of the Growth Kinetics of Elementary Spiral Steps on Ice Basal Faces Grown from Water Vapor

Abstract

We measured the velocity Vstep of isolated elementary spiral steps and the distance Leq between adjacent equivalent spiral steps on ice basal faces by advanced optical microscopy. We determined the step kinetic coefficient β from Vstep measured under various supersaturations. We performed similar experiments under various temperatures T, and determined the temperature dependence of β of ice basal faces, for the first time, in the temperature range of −26.0 to −2.7 °C. When −6.2 ≤ T ≤ −2.7 °C, the value of β decreased significantly with decreasing T. In contrast, when −15.0 ≤ T ≤ −6.2 °C, the value of β increased with decreasing T, and had the maximum at T ≈ −15 °C. When −26.0 ≤ T ≤ −15.0 °C, the value of β decreased monotonically with decreasing T. Such complicated temperature dependence of β strongly implies the existence of unknown phenomena in the temperature range examined. To obtain a clue to the complicated behavior of β, we also measured dependence of Leq on surface supersaturation Δμsurf. When −13.0 ≤ T ≤ −3.2 °C, plots of Leq vs 1/Δμsurf satisfactorily follow the spiral growth model. However, when −26.0 ≤ T ≤ −15.0 °C, the Leq vs 1/Δμsurf plots do not follow any model: this temperature range agrees with the temperature range in which β decreased monotonically with decreasing T.