A molecular-beam study of the collision dynamics of methane and ethane upon a graphitic monolayer on Pt(111)
A molecular-beam study of the collision dynamics of methane and ethane upon a graphitic monolayer on Pt(111)
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DOI：
10.1063/1.2046631
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发表时间：
2005-09-15
影响因子：
4.4
通讯作者：
Yamamoto, S
中科院分区：
文献类型：
--
作者：
Kondo, T;Mori, D;Yamamoto, S
利用超声速分子束散射技术，测量了从Pt（111）上的惰性高取向单层石墨（MG）上散射的烷烃分子（CH4和C2H6）的角强度分布。在Pt（111）表面覆盖完整的单分子层的MG，由于烷烃分子相对于MG的大质量比，在与表面碰撞时通过声子产生大量的烷烃能量损失。基于经典的立方体模型，仅适用于无内模激发的分子，利用稀有气体原子散射数据确定了MG 76（6个碳原子）和Pt(111) 585（3个铂原子）的有效质量。尽管CH4和稀有气体原子之间的自由度不同，但由于CH4结构的高度对称性，发现简单的硬立方模型可以很好地描述CH4的散射。利用最近发展的椭球-搓板模型（硬立方体模型的扩展，除了表面波纹外，还包括一些碰撞分子的内模激励）发现，与CH4不同，C2H6的侧轮旋转模式在碰撞过程中被显著激发，而直升机模式的激励在平坦的MG表面上可以忽略不计。(c) 2005年美国物理研究所。
Utilizing a supersonic molecular-beam scattering technique, the angular intensity distributions of alkane molecules (CH4 and C2H6) have been measured, which are scattered from a chemically inert and highly oriented monolayer graphite (MG) on Pt(111). A MG which covers the Pt(111) surface with a full monolayer is found to induce a large energy loss of alkanes during collision with the surface by phonon creation due to the large mass ratio of an alkane molecule with respect to MG. Based on the classical cube model, only applicable to the molecules without internal mode excitation, the effective masses of MG of 76 (six atoms of carbon) and Pt(111) of 585 (three atoms of platinum) are determined from rare-gas atom scattering data. Despite the difference in the degree of freedom between CH4 and rare-gas atoms, CH4 scattering is found to be well described by the simple hard-cube model as a result of the high symmetry of the CH4 structure. With the recently developed ellipsoid-washboard model, an extension of the hard-cube model to include some internal mode excitation of impinging molecules in addition to the surface corrugation, it is found that unlike CH4 the cartwheel rotation mode of C2H6 is significantly excited during collision, while the helicopter mode excitation is negligible on a flat MG surface. (c) 2005 American Institute of Physics.