Dissipation of translational energy of molecules on surfaces

2006年，我们利用超音速分子束仪结合超高真空室进行了固体表面上吸附质扩散的实验。通过对阶梯Pt（997）表面暴露于CO分子和能控的Ne或Ar原子后的傅里叶变换红外光谱的分析，得到了CO在阶梯和阶梯上的扩散活化能。2007年，我们利用碰撞诱导扩散现象考察了表面吸附物在扩散过程中平动能弛豫的机理，结果如下：将Pt（997）表面暴露于覆盖0.033 ML的CO分子后，暴露于具有平动能的Ne或Ar原子。如果作用于台阶位置的CO分子的摩擦力较低，则在碰撞产生足够高的动能后，它们可以长距离迁移。如果摩擦力大，它们会在碰撞后立即停止。然后，根据CO分子与稀有气体原子碰撞后的分布，可以估算出CO分子的摩擦力。但由于CO分子的平动能及其方向取决于CO分子与稀有气体原子碰撞时的排列，我们采用了分子动力学计算，并将计算结果与实验结果进行了比较。通过比较，CO在Pt表面的摩擦系数估计为8x10^<12> sec^<-1>。

In 2006, we have performed the experiment about the adsorbate diffusion on solid surfaces by using super sonic molecular beam apparatus combined with ultra high vacuum chamber. From the analysis of the Fourier transformed infrared spectra obtained after a stepped Pt(997) surface was exposed to CO molecules and subsequently to energy-controlled Ne or Ar atoms, the activation energy of the diffusion of CO adsorbed at terrace site and step site were obtained.In 2007, we examined the mechanism of the relaxation of the translational energy of adsorbates on surfaces during the diffusion process by the use of collision induced diffusion phenomena as follows: After a Pt(997) surface was exposed to CO molecules with a coverage of 0.033 ML, it was exposed to Ne or Ar atoms with a translational energy. If the friction applied to CO molecules at terrace site is low, they can migrate long distances after a collision imparts a sufficiently high kinetic energy. If the friction is large, they will stop immediately after the collision. Then, the friction can be estimated from the distribution of CO molecules after the collision with rare gas atoms. However, since the translational energy of CO molecule and its direction depend on the arrangement of the CO molecule and the rare gas atom upon the collision, we employed molecular dynamics calculation and the calculational results were compared with experimental results. From the comparison, the friction coefficient of CO on the Pt surface was estimated to be 8x10^<12> sec^<-1>.