标题： CO冰光解吸：波长依赖性研究 显示英文标题

标题： CO ice photodesorption: A wavelength-dependent study

摘要： 紫外线诱导的冰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冷分子气体的存在。 对于天体物理上有重要意义的冰的平均紫外线光解吸产率，已有宽带紫外线灯实验的信息。 然而，低质量前主序星周围的紫外线场、冲击波周围以及许多其他天体物理环境中的紫外线场通常主要由离散的原子和分子发射线组成。 因此，考虑光解吸产率和机制的波长依赖性是至关重要的。 在本研究中，首次探索了纯CO冰在90至170 nm波长范围内的波长依赖性光解吸。 实验是在超高真空条件下进行的，使用可调谐同步辐射。 通过冰的反射模式红外吸收光谱和气相四极质谱同时探测冰的光解吸。 CO的实验结果显示出强烈的波长依赖性，这直接与CO冰的振动电子跃迁强度相关，意味着光解吸是由电子跃迁引起的（DIET）。 观察到的冰吸收光谱依赖性表明，在121.6 nm（Ly-alpha）处的光解吸产率相对较低，因为CO在此处几乎不吸收，而与CO第一电子态（单重Pi态在150 nm）跃迁对应的波长处则发现了较高的产率；CO的光解吸速率强烈依赖于不同恒星形成环境中遇到的紫外线轮廓。 显示英文摘要

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.