Dalgarno A
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 2006 Aug 15;103(33):12269-73. doi: 10.1073/pnas.0602117103. Epub 2006 Aug 7.
The chemistry that occurs in the interstellar medium in response to cosmic ray ionization is summarized, and a review of the ionization rates that have been derived from measurements of molecular abundances is presented. The successful detection of large abundances of H(3)(+) in diffuse clouds and the recognition that dissociative recombination of H(3)(+) is fast has led to an upward revision of the derived ionization rates. In dense clouds the molecular abundances are sensitive to the depletion of carbon monoxide, atomic oxygen, nitrogen, water, and metals and the presence of large molecules and grains. Measurements of the relative abundances of deuterated species provide information about the ion removal mechanisms, but uncertainties remain. The models, both of dense and diffuse clouds, that are used to interpret the observations may be seriously inadequate. Nevertheless, it appears that the ionization rates differ in dense and diffuse clouds and in the intercloud medium.
总结了星际介质中因宇宙射线电离而发生的化学反应，并对从分子丰度测量中得出的电离率进行了综述。在弥漫云中成功检测到大量的H₃⁺，以及认识到H₃⁺的离解复合速度很快，导致了所推导的电离率向上修正。在致密云中，分子丰度对一氧化碳、原子氧、氮、水和金属的消耗以及大分子和尘埃的存在很敏感。氘化物种相对丰度的测量提供了有关离子去除机制的信息，但仍存在不确定性。用于解释观测结果的致密云和弥漫云模型可能严重不足。然而，似乎致密云和弥漫云以及云间介质中的电离率是不同的。
