H2, HD, and D2 abundances on ice-covered dust grains in dark clouds
H2, HD, and D2 abundances on ice-covered dust grains in dark clouds
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DOI：
10.1051/0004-6361/200912124
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发表时间：
2011-03-01
影响因子：
6.5
通讯作者：
Lemaire, J. -L.
中科院分区：
文献类型：
--
作者：
Kristensen, L. E.;Amiaud, L.;Lemaire, J. -L.
目标。我们试图研究星际介质中暗分子云中冰覆盖的尘埃颗粒上吸附的 H-2、HD 和 D-2 的丰度。方法。我们使用之前开发的详细模型来描述 H-2 及其同位素体在水冰上的程序升温解吸 (TPD) 实验。我们在这里将这些模型结果从实验室条件推断到类似于暗分子云中发现的条件。结果。通过我们的模型，我们能够推断出三个重要结果。 (i) H-2 和同位素体在尘埃颗粒上积聚的时间尺度小于 10(4) 年。 (ii) 由于 D-2 相对于 HD 具有更高的结合能，D-2 成为晶粒上最丰富的氘化物质，其含量比 HD 多约 50%（是 H-2 的 10(-5) 的几倍）。 (iii) D-2 的表面覆盖度作为温度的函数表明，在非常低的温度（即低于 10 K）下，D-2 可能比 HD 丰富两个数量级。当水通过 OH 和 H-2 之间的反应形成时，讨论了水在颗粒表面氘化的可能影响。
Aims. We seek to study the abundances of H-2, HD, and D-2 adsorbed onto ice-covered dust grains in dark molecular clouds in the interstellar medium.Methods. We use our previously developed detailed model describing temperature-programmed desorption (TPD) experiments of H-2 and its isotopologues on water ice. We here extrapolate these model results from laboratory conditions to conditions similar to those found in dark molecular clouds.Results. By means of our model we are able to infer three important results. (i) The time scale for H-2 and isotopologues to accrete onto dust grains is less than 10(4) yrs. (ii) Due to the higher binding energy of D-2 with respect to HD, D-2 becomes the most abundant deuterated species on grains by similar to 50% with respect to HD (a few times 10(-5) with respect to H-2). (iii) The surface coverage of D-2 as a function of temperature shows that at very low temperatures (i. e., less than 10 K), D-2 may be two orders of magnitude more abundant than HD. Possible implications for deuteration of water on grain surfaces are discussed when it forms through reactions between OH and H-2.