Ly-alpha photon induced amorphization of Ic water ice at 16 Kelvin. Effects and quantitative comparison with ion irradiation
Ly-alpha photon induced amorphization of Ic water ice at 16 Kelvin. Effects and quantitative comparison with ion irradiation
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Ly-α 光子在 16 开尔文引起 Ic 水冰的非晶化。
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
G. Baratta
中科院分区：
文献类型：
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作者：
G. Leto;G. Baratta
水冰是太空中、行星及其卫星表面、彗星和星际尘埃颗粒中无处不在的物质。水冰的结构很大程度上取决于沉积温度。如果在低温（即16 K）下沉积，它可以是非晶的，或者如果沉积温度高于140 K，它可以是结晶的。本文首次报道了用原位红外光谱法对莱曼- α紫外光子在结晶水冰中引起的结构效应进行的实验研究。在相同的实验装置上，比较了莱曼- α光解和离子辐照的效应。我们发现，正如在快离子的情况下已经观察到的那样，UV莱曼- α光子也能够在每个分子几eV的剂量后完全非晶化结晶水冰结构。这项研究具有重要的天体物理学意义，特别是因为光子和快离子都存在于太空中，它们可以引起3 μ m晶冰带轮廓的变化。因此，当人们试图从观测到的冰带的轮廓中推断出有关责任尘埃的物理状态（例如温度历史）的信息时，必须考虑这些影响。
Water ice is a ubiquitous material in space, on the surface of planets and their moons, in comets and interstellar dust grains. The structure of water ice strongly depends on the deposition temperature. It can be amorphous if deposited at low temperature, i.e. 16 K, or crystalline if the deposition temperature is higher than 140 K. In this paper we report the first experimental study of the structural effects induced by Lyman- α UV photons in crystalline water ice carried out by in situ infrared spectroscopy. The effects induced by Lyman- α photolysis are compared with those induced by ion irradiation carried out with the same experimental apparatus. We found that, as already observed in the case of fast ions, also UV Lyman- α photons are able to fully amorphize the crystalline water ice structure after a dose of few eV per molecule. This study has important astrophysical implications, in particular because photons and fast ions are both present in space, they can induce variations in the profile of the 3 μ m band of crystalline water ice. Thus these effects have to be considered when one attempt to deduce information on the physical status (e.g. temperature history) of the responsible dust from the profile of the observed ice band.