The correlation between the inclination of surface reaction sites and the spatial distribution of desorbing product molecules

1.本课题以反应位的倾斜为重点，在Pt（110）（1x 2）台阶表面上测量了CO氧化脱附产物CO_2的空间分布。（阶地的倾斜角度：35.2度）、Ir（110）（1x 2）（35.2度）、Pt（112）（19.5度）、Pt（335）（14.4度）和Pt（557）（9.5度），以检查倾斜度在空间分布中保持的准确程度。在空间分布上，该角度已被证实保持在约85%。这意味着空间分布测量对于识别反应位点是有力的。随着反应覆盖率的增加，在上述台阶表面上加热CO和O2的粘合层所引起的CO_2生成扩展到较低的温度，在150-400 K范围内产生多个峰，并分别分析了各峰的空间分布和速度分布。CO_2解吸的平动温度在解吸角最大时达到最大值，随着解吸角的增大，平动温度迅速降低。这表明了空间分布被锐化的机制，即，解吸产物的速度分量在反应位点的法线方向上增强.随着反应物覆盖率的增加，反应位点由平台向台阶或沟槽扩展。在高覆盖度下，未在阶地法线中准直的解吸分量增加。

1. In this project focused on the inclination of the reaction sites, the spatial distributions of desorbing product CO_2 in the CO oxidation are measured on several stepped platinum surfaces, Pt(110)(1x2)(the inclining angle of terraces : 35.2ﾟ), Ir(110)(1x2)(35.2ﾟ), Pt(112)(19.5ﾟ), Pt(335)(14.4ﾟ) and Pt(557)(9.5ﾟ), to examine how accurately the inclination is preserved in the spatial distributions. The angle has been confirmed to be preserved to about 85% in the spatial distribution. This means that the spatial distribution measurements are powerful to identify reaction sites.2. The CO_2 formation induced by heating the coadlayr of CO and oxygen on the stepped surfaces mentioned above is extended to lower temperatures, with increasing the reaction coverages, yielding several peaks in the range of 150-400 K.The spatial and velocity distributions of each peak have been separately analyzed. The translational temperature of desorbing CO_2 is maximized at the desorption angle where the flux is maximized and decreases quickly with increasing the shift of the angle. This indicates the mechanism in which the spatial distribution is sharpened, i.e., the velocity component of desorbing product is enhanced in the normal direction of the reaction sites.3. The reaction sites are extended from the terraces to steps or into surface troughs when the reactant coverages are increased. The desorption component not collimated in the terrace normal is increased at high coverages.