Lazer spectroscopic study on vibrutional excitation of NO on alkalated Si surfaces.

用分子束方法结合俄歇电子能谱和REMPI检测，研究了碱金属(K原子和Cs原子)促进NO吸附在Si(100)表面的过程。观测到的粘附率S与碱的相关性很好，说明碱的促进作用是局部的。用俄歇电子能谱观测到的S的衰变随NO剂量的变化与用REMPI得到的直接非弹性散射强度的演化成反相关。这一事实被理解为：由于直接非弹性散射大多发生在与表面的单次碰撞过程中，局部碱促进是在入射NO分子与碱金属吸附的单次碰撞中实现的。然后，通过引入反应截面，模拟了S的衰变随NO剂量的变化。估算的反应半径与K原子的共价半径相近，但略大于K原子的共价半径，且随Rheta_K的增大而增大。碱促进作用可用非电离碱原子向NO分子亲和力水平的电荷转移来解释，其基础是E_F周围的吸附原子态密度。

Alkali-metal (K and Cs adatoms) promotion of NO sticking on Si (100) has been studied using a molecular beam method combined with AES and REMPI detection. The observed sticking probability S shows a good correlation with rheta_<alkali>, indicating that the alkali promotion is local in nature. The decay of S as a function of NO dose as observed with AES shows an anti-correlation with the evolution of the direct-inelastic scattering intensity as obtained with REMPI. This fact is understood as follows : since the direct-inelastic scattering occurs mostly in a single collision process with the surface, local alkali promotion is realized in a single collision of the incident NO molecule with the alkali-metal adsorbates. The decay of S as a function of NO dose is then simulated by introducing a reaction cross section. The evaluated reaction radii are almost eaual to but somewhat larger than the covalent radius of a K atom, with a increasing trend with rheta_K. The alkali promotion is explained in terms of electron charge transfer from the non-ionized alkali adatoms to the affinity level of NO molecules based on the adatom density of state around E_F.