Assignment and identification of reaction sites on solid surfaces

比较了两种阶梯铂表面上CO的热解吸动力学和光解解吸动力学，即pt（113）由具有（111）结构的两原子宽阶梯和具有（001）结构的单原子高阶梯组成，pt（112）具有（111）结构的三原子宽阶梯。在193 nm和308 nm照射下，CO_2的解吸动力学没有差异。在Pt（113）和Pt(133) 1上分析了氧取向。氧取向，用NEXAFS检测。admolecule沿着Pt（113）上的槽，而其在Pt（133）上的取向在高覆盖率时从平行槽偏移。在低O_2和CO覆盖率的Pt（113）上，高速CO_2解吸沿槽沿平面有两个方向准直。沿着槽发射的氧原子与CO相互作用，产生与热反应不同的位点。速度分析也证实了这一快速组分的存在。沿台阶（29.5）和台阶（-25.2）正线的CO_2脱附在高O_2覆盖率下得到加强。Pt(112) 3也观察到阶地解吸。热氧化，解吸产物的空间分布和速度分布即使在热氧化中，当产物被排斥解吸时，也能产生位点的结构信息。场地从露台移至CO覆盖率更高的台阶。CO_2解吸的特征为：(1)准直方向偏离位正方向约30%，(2)各向异性角分布与位对称有关，(3)高的平动温度表明排斥性解吸，但在光解反应中约占一半，(4)台阶与阶地之间CO_2平动温度无显著差异。

A comparison of product desorption dynamics between thermally and photolytically CO oxidation was performed on two stepped platinum surfaces, i.e., pt (113) consisting of two-atom wide terraces with a (111) structure and one-atom high stpes with a (001) structure, and Pt (112) with three-atom wide terraces of a (111) structure. No difference is in the CO_2 desorption dynamics in the usage of 193 nm and 308 nm irradiation. The oxygen orientation was analyzed on Pt (113) and also on Pt (133).1. Oxygen orientation, It was examined by NEXAFS.The admolecule lies along the trough on Pt (113), whereas its orientation on Pt (133) is shifted from the trough parallel at high coverages.2. Photolytic oxidation, The CO_2 desorption with high velocity is collimated in two directional ways in a plane along the trough on Pt (113) at low O_2 and CO covergaes. Oxygen atoms emitted along the trough interact with CO,yielding the sites different from the thermal reaction. The velocity analysis also confirms the presence of this fast component The CO_2 desorption collimated along the terrace (29.5ﾟ) and step (-25.2ﾟ) normal is enhanced at high O_2 coverages. The terrace desorption is also observed on Pt (112).3. Thermal oxidation, The spatial and velocity distributions of desorbing product yield the structural information of the sites even in the thermal oxidation, when the product is repulsively desorbed. The site is moved from the terrace to the step at higher CO coverage. The CO_2 desorption is characterized as (1) the collimation is shifted about 30% from the site normal, (2) anisotropic angular distribution is correlated to the site symmetry, (3) high translational temperature indicates repulsive desorption but about half of the value in the photolytic reaction, and (4) no significant difference in the translational temperature of CO_2 between the terrace and step.