气相存在下过渡金属表面脱附动力学机理的研究

A Study on the Mechanism of Desorption fromTransition-Metal Surface under a Gas Ambience

作者利用同位素跳跃技术来探讨气相压强促进过渡金属表面吸附分子脱附这一新现象的机理。获得了３５３Ｋ下饱和吸附Ｃ１６Ｏ的Ｒｅ（０００１）表面的超高真空等温脱附和不同气相压强的同位素Ｃ１８Ｏ交换的谱图。从相对覆盖度及其对数随时间的变化曲线可以看出，真空等温脱附过程为一级动力学过程。而在气相同位素存在下交换脱附过程可用一级加二级来近似，拟合的结果与实验符合很好。作者还发现了交换速率远大于真空等温脱附速率，而且随压强的增加而增加，这说明气相压强直接促进了表面吸附分子的脱附。

This paper,with the help of isotope witch technique,studied the desorption kinetics of C16O/Re(0001) in the presence of a C18O isotope gas ambience.It is found that the desorption rate at a constant pressure of C18O declines nonlinearly with the surface coverage of C16O and it implies nonlinear kinetics for the C16O/C18O exchange process.The initial desorption rate is,however,linearly dependent on the pressure of C18O.A concerted adsorption-desorption mechanism is postulated which involves a dynamic feature of mutual screening between coadsorbed isotopic species on the surface to interprete the nonlinear desorption inetics under a gas ambience.