Lu Haiping, McCartney Stephanie A, Sadtchenko Vlad
Department of Chemistry, George Washington University, 725 21st St. NW, Rm. 107, Washington, DC 20052, USA.
J Chem Phys. 2009 Feb 7;130(5):054501. doi: 10.1063/1.3039077.
We report the results of a fast thermal desorption spectroscopy study of the H/D isotopic exchange kinetics in a few micrometer thick, pure polycrystalline ice film and in ice films doped with HCl. Using the isotopic exchange reaction as a probe of transport processes in ice, we determined the effective H/D interdiffusion coefficients, D(eff), in pure and doped polycrystalline ice at temperatures ranging from -18 to -1 degree C. In the case of pure polycrystalline ice, D(eff) demonstrates an Arrhenius dependence on temperature with an effective activation energy of 69+/-3 kJ mol(-1) and a pre-exponential of 10(9+/-0.5) microm(2) ms(-1) up to -2 degrees C. According to our analysis, H/D interdiffusion coefficient at the grain boundaries also shows an Arrhenius dependence on temperature with an activation energy of 69+/-3 kJ mol(-1) and a pre-exponential of 10(11+/-1) microm(2) ms(-1). However, the addition of 0.04% of HCl results in a marked deviation of D(eff) from Arrhenius law at -8 degrees C, which is attributed to premelting at intersections of grain boundaries. We discuss the structure and transport properties of condensed aqueous phase at grain boundaries in polycrystalline ice at various temperatures.
我们报告了一项快速热脱附光谱研究的结果，该研究针对几微米厚的纯多晶冰膜以及掺杂了HCl的冰膜中的H/D同位素交换动力学。利用同位素交换反应作为冰中传输过程的探针，我们测定了在-18至-1摄氏度温度范围内纯多晶冰和掺杂多晶冰中的有效H/D互扩散系数D(eff)。对于纯多晶冰，在-2摄氏度以下，D(eff)表现出对温度的阿仑尼乌斯依赖性，有效活化能为69±3 kJ mol(-1)，指前因子为10(9±0.5) μm(2) ms(-1)。根据我们的分析，晶界处的H/D互扩散系数也表现出对温度的阿仑尼乌斯依赖性，活化能为69±3 kJ mol(-1)，指前因子为10(11±1) μm(2) ms(-1)。然而，添加0.04%的HCl会导致在-8摄氏度时D(eff)明显偏离阿仑尼乌斯定律，这归因于晶界交汇处的预熔化。我们讨论了多晶冰在不同温度下晶界处凝聚水相的结构和传输性质。
