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arXiv 1109.0281astro-ph.GA
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CO冰光解吸：波长依赖性研究

CO ice photodesorption: A wavelength-dependent study

Edith C. Fayolle, Mathieu Bertin, Claire Romanzin, Xavier Michaut, Karin I. Oberg, Harold Linnartz, Jean-Hugues Fillion

备注：
5 pages, 2 figures, published in ApJL
发表信息：
ApJ 739 L36 (2011)
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摘要：

冰的紫外光诱导光解吸是一种非热蒸发过程，可以解释在一系列星际区域中存在冷分子气体。关于天体物理学上重要的冰的平均紫外光解吸产率的信息存在于宽带紫外灯实验中。然而，低质量前主序星周围、激波周围和许多其他天体物理环境中的紫外线场通常由离散的原子和分子发射线主导。因此，至关重要的是要考虑光解吸产率和机制的波长依赖性。在这项工作中，第一次，纯CO冰的波长依赖的光脱附探索90和170 nm之间。实验在超高真空条件下进行，使用可调谐同步辐射。冰的光解吸同时探测红外吸收光谱的反射模式的冰和气相的四极质谱。CO的实验结果揭示了一个强烈的波长依赖性直接链接到CO冰的电子振动跃迁强度，这意味着光脱附诱导的电子跃迁（DIET）。所观察到的依赖于冰的吸收光谱意味着相对较低的光解吸产率在121.6 nm（Ly-alpha），其中CO几乎没有吸收，相比之下，发现在波长符合过渡到CO的第一电子态（单线态Pi在150 nm）的高产率; CO的光解吸率强烈依赖于在不同的恒星形成环境中遇到的紫外线配置文件。

英文摘要：

UV-induced photodesorption of ice is a non-thermal evaporation process that can explain the presence of cold molecular gas in a range of interstellar regions. Information on the average UV photodesorption yield of astrophysically important ices exists for broadband UV lamp experiments. UV fields around low-mass pre-main sequence stars, around shocks and in many other astrophysical environments are however often dominated by discrete atomic and molecular emission lines. It is therefore crucial to consider the wavelength dependence of photodesorption yields and mechanisms. In this work, for the first time, the wavelength-dependent photodesorption of pure CO ice is explored between 90 and 170 nm. The experiments are performed under ultra high vacuum conditions using tunable synchrotron radiation. Ice photodesorption is simultaneously probed by infrared absorption spectroscopy in reflection mode of the ice and by quadrupole mass spectrometry of the gas phase. The experimental results for CO reveal a strong wavelength dependence directly linked to the vibronic transition strengths of CO ice, implying that photodesorption is induced by electronic transition (DIET). The observed dependence on the ice absorption spectra implies relatively low photodesorption yields at 121.6 nm (Ly-alpha), where CO barely absorbs, compared to the high yields found at wavelengths coinciding with transitions into the first electronic state of CO (singulet Pi at 150 nm); the CO photodesorption rates depend strongly on the UV profiles encountered in different star formation environments.

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