Interaction of atomic and molecular deuterium with a nonporous amorphous water ice surface between 8 and 30 K
Interaction of atomic and molecular deuterium with a nonporous amorphous water ice surface between 8 and 30 K
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DOI：
10.1063/1.2746323
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发表时间：
2007-10-14
影响因子：
4.4
通讯作者：
Lemaire, J. L.
中科院分区：
文献类型：
--
作者：
Amiaud, L.;Dulieu, F.;Lemaire, J. L.
在低温下，氢与覆盖着冰的尘埃颗粒的分子和原子相互作用是暗星际云中星星形成和化学反应的关键机制。我们已经实验研究了原子和分子氘在无孔无定形水冰表面8和30 K之间的相互作用，在兼容的条件下外推到一个天体物理背景。D-2的吸附能呈现出一个广泛的分布，已经观察到的多孔水冰表面。在低覆盖度下，D-2的粘附系数随着已经吸附在表面上的氘分子的数量线性增加。原子D的分解通过将分子释放到气相中的快速反应发生。部分新形成的分子处于振动激发态（v=1-7）。原子复合效率随着已经吸附在水冰上的D-2分子的存在而增加，这可能是因为这些分子增加了原子的粘附系数，就像入射D-2的情况一样。我们已经测量了在已经吸收的D-2存在下的原子复合效率，因为它预计会发生在星际介质中。复合效率随温度的升高而迅速下降，在13 K时为零.这使我们能够估计的上限值的原子吸附能E-a类似于29毫电子伏，与以前的计算。(C)2007年，美国物理学会。
Molecular and atomic interactions of hydrogen on dust grains covered with ice at low temperatures are key mechanisms for star formation and chemistry in dark interstellar clouds. We have experimentally studied the interaction of atomic and molecular deuterium on nonporous amorphous water ice surfaces between 8 and 30 K, in conditions compatible with an extrapolation to an astrophysical context. The adsorption energy of D-2 presents a wide distribution, as already observed on porous water ice surfaces. At low coverage, the sticking coefficient of D-2 increases linearly with the number of deuterium molecules already adsorbed on the surface. Recombination of atomic D occurs via a prompt reaction that releases molecules into the gas phase. Part of the newly formed molecules are in vibrationally excited states (v=1-7). The atomic recombination efficiency increases with the presence of D-2 molecules already adsorbed on the water ice, probably because these increase the sticking coefficient of the atoms, as in the case of incident D-2. We have measured the atomic recombination efficiency in the presence of already absorbed D-2, as it is expected to occur in the interstellar medium. The recombination efficiency decreases rapidly with increasing temperature and is zero at 13 K. This allows us to estimate an upper limit to the value of the atom adsorption energy E-a similar to 29 meV, in agreement with previous calculations. (C) 2007 American Institute of Physics.