CO冰的光脱附
Photodesorption of CO ice
摘要：
在恒星形成区的高密度和低温下，除了H2之外的所有分子都应该在短于云寿命的时间尺度上粘附在尘埃颗粒上。然而，这些云被检测到在毫米线的气态CO。在这些温度下，热解吸是可以忽略不计的，因此，非热解吸机制是必要的，以保持分子在气相中。本文首次在实验室研究了超高真空下纯CO冰的光脱附，在15 K时，每UV（7- 10.5eV）光子的脱附速率为3E-3CO分子。这一速率比先前估计的速率大1 E2 - 1 E5倍，与其他非热解吸速率的估计值相当。实验结果表明，该机制是冰表面分子的单光子脱附过程。该过程的测量效率表明，CO光脱附在防止气体中分子完全去除方面的作用被低估了。
英文摘要：
At the high densities and low temperatures found in star forming regions, all molecules other than H2 should stick on dust grains on timescales shorter than the cloud lifetimes. Yet these clouds are detected in the millimeter lines of gaseous CO. At these temperatures, thermal desorption is negligible and hence a non-thermal desorption mechanism is necessary to maintain molecules in the gas phase. Here, the first laboratory study of the photodesorption of pure CO ice under ultra high vacuum is presented, which gives a desorption rate of 3E-3 CO molecules per UV (7-10.5 eV) photon at 15 K. This rate is factors of 1E2-1E5 larger than previously estimated and is comparable to estimates of other non-thermal desorption rates. The experiments constrains the mechanism to a single photon desorption process of ice surface molecules. The measured efficiency of this process shows that the role of CO photodesorption in preventing total removal of molecules in the gas has been underestimated.
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