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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mixing of the Immiscible: Hydrocarbons in Water-Ice near the Ice Crystallization Temperature
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Mixing of the Immiscible: Hydrocarbons in Water-Ice near the Ice Crystallization Temperature

机译：混溶：冰冰温度附近冰水中的碳氢化合物混合

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摘要

Structural changes in hydrocarbon-doped water-ice during amorphous to crystalline phase conversion are investigated using polycyclic aromatic hydrocatbons (PARS) as probes. We show that aggregation of impurity molecules occurs due to the amorphous crystalline transition in ice, especially when they are hydrophobic molecules such as PAHs. Using ultraviolet visible (UV vis), Fourier-transform Infrared (FTIR), and laser-induced-fluorescence (LIP) spectroscopic techniques, we show that, although ice infrared absorption features change from a broad structureless band corresponding to amorphous ice to a sharp structured crystalline ice bands, simultaneously, sharper isolated PAH UV absorption features measured in the amorphous ice host turn broad upon ice crystallization. A simultaneous decrease in the monomer fluorescence and increase in the excimer emission band is observed, a clear indication for the formation of PAR molecular aggregates when amorphous ice is converted to crystalline ice at higher temperatures. Similar to the irreversible amorphous crystalline phase transitions, the UV, fluorescence, and excimer,emissions indicate that PAH's undergo irreversible aggregation. Our studies suggest that organic impurities exist as aggregates rather than monomer's trapped in crystalline water-ice when cycled through temperatures that convert amorphous ice to crystalline ice, rendering a better insight into phenomena such as the formation of cometary crust. This aggregate formation also may significantly change the secondary reaction pathways and rates in impurity-doped ices in the lab, on Earth, in the solar system, and in the interstellar medium.
机译：使用多环芳香烃（PARS）作为探针，研究了非晶态到结晶态转化过程中碳氢化合物掺杂的水冰的结构变化。我们表明，杂质分子的聚集是由于冰中的无定形晶体转变而发生的，特别是当它们是疏水分子（如PAHs）时。使用紫外可见光（UV vis），傅立叶变换红外（FTIR）和激光诱导荧光（LIP）光谱技术，我们显示，尽管冰的红外吸收特征从对应于非晶冰的宽无结构带变为锐利的同时，在无定形冰宿主中测得的更清晰的分离的PAH UV吸收特征在冰晶化后变得宽泛。观察到单体荧光同时减少，并且准分子发射谱带增加，这清楚地表明了在较高温度下无定形冰转化为结晶冰时，PAR分子聚集体的形成。类似于不可逆的无定形结晶相变，紫外线，荧光和受激准分子的发射表明PAH经历了不可逆的聚集。我们的研究表明，有机杂质在通过将无定形冰转化为结晶冰的温度循环时，会以聚集体的形式存在，而不是被困在结晶水冰中的单体，从而更好地洞察了诸如彗星结壳的形成。这种聚集体的形成也可能会显着改变实验室，地球，太阳系和星际介质中掺杂杂质的冰的次级反应途径和速率。

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