Quantum study of Eley-Rideal reaction and collision induced desorption of hydrogen atoms on a graphite surface. II. H-physisorbed case.
Quantum study of Eley-Rideal reaction and collision induced desorption of hydrogen atoms on a graphite surface. II. H-physisorbed case.
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DOI：
10.1063/1.2177655
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发表时间：
2006-03
期刊：
影响因子：
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通讯作者：
R. Martinazzo;G. Tantardini
中科院分区：
文献类型：
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作者：
R. Martinazzo;G. Tantardini
在前人研究了氢原子在石墨表面化学吸附的碰撞诱导过程之后[R. Martinazzo和G. F. Tantardini，J.Chem.Phys.124，124702（2006）]，在此考虑目标氢原子最初物理吸附在表面上的情况。几个被认为是在物理吸附阱中的目标H原子的吸附物-衬底初始状态，和CI过程中的弹丸能量高达1 eV的研究。结果表明：（i）低碰撞能下的Eley-Rideal截面可能大于H-化学吸附时的截面，但随着碰撞能的增加，它们迅速减小;（ii）产物氢分子振动非常兴奋;（iii）碰撞诱导脱附截面迅速增加，达到大于10 A ~ 2的饱和值;（iv）入射原子的捕获被发现在低能量下与Eley-Rideal反应一样有效，并且在高能量下保持相当大的（3-4 A2）。后一种吸附物诱导的捕获主要导致亚稳态热氢原子的形成，即，具有多余能量的原子在平行于表面的运动中被引导。这些原子可能有助于解释石墨上氢的形成。
Following previous investigation of collision induced (CI) processes involving hydrogen atoms chemisorbed on graphite [R. Martinazzo and G. F. Tantardini, J. Chem. Phys. 124, 124702 (2006)], the case in which the target hydrogen atom is initially physisorbed on the surface is considered here. Several adsorbate-substrate initial states of the target H atom in the physisorption well are considered, and CI processes are studied for projectile energies up to 1 eV. Results show that (i) Eley-Rideal cross sections at low collision energies may be larger than those found in the H-chemisorbed case but they rapidly decrease as the collision energy increases; (ii) product hydrogen molecules are vibrationally very excited; (iii) collision induced desorption cross sections rapidly increase, reaching saturation values greater than 10 A2; (iv) trapping of the incident atoms is found to be as efficient as the Eley-Rideal reaction at low energies and remains sizable (3-4 A2) at high energies. The latter adsorbate-induced trapping results mainly in formation of metastable hot hydrogen atoms, i.e., atoms with an excess energy channeled in the motion parallel to the surface. These atoms might contribute in explaining hydrogen formation on graphite.