Development of an apparatus for the analysis of chemical reactions on surfaces equipped with a Helium beam apparatus.

本项目的目的是开发一种应用超声分子束技术来观察表面反应和表面结构的装置。该装置由分子束装置、控制样品位置的机械手、旋转质谱仪、真空室和抽运系统组成。分子束装置在三次差动抽运和分子平动能控制方面工作良好。在机械手方面，采用超高压用步进电机，可以对样品进行高精度控制，这是氦束散射实验所需要的。旋转质谱仪和为减少背景气体而构建的双差分泵系统围绕样品旋转。通过进行下面的实验，我们确定了该装置的足够的性能。1.我们进行了He衍射实验。我们观察到当He光束指向样品时，从表面散射的He原子角分布中与LiF(100)表面结构相对应的衍射图。2.我们观察到He光束在Ni(100)表面的镜面反射强度随着吸附量的增加而减小。3.我们观察到CO和NH_3在Ni(100)表面上的亚单层吸附光谱。

The purpose of this project is to develop an apparatus with which surface reactions and surface structures can be observed, by applying the techniques of supersonic molecular beam. With the apparatus, we want to control the surface reaction by varying the translational energy of molecules impinging on the surface, and observe the property of the reaction using the Helium beam scattering technique.The apparatus is composed of a molecular beam apparatus, a manipulator with which the position of the sample is controlled, a rotatable mass spectrometer, a vacuum chamber and a pumping system.The molecular beam apparatus is working well in point of the triply differential pumping and the control of the translational energy of molecules. As to the manipulator, by the use of stepping motors for use in UHV,the sample can be controlled with high precision which is needed for the experiment of He beam scattering. The rotatable mass spectrometer and a double differential pumping system constructed to reduce the background gas are rotated around the sample.By performing the experiments described below, we ascertained the enough performance of the apparatus.1.We performed He diffraction experiment. We observed the diffraction pattern corresponding to LiF (100) surface structure in the angular distribution of He atoms scattered from the surface when He beam is directed to the sample. We confirmed that the surface structure is measured by the use of He beam.2.We observed that the intensity of specular reflection of He beam from Ni (100) surface decrease with increasing the amount of the adsorbate.3.We observed spectra of submonolayr CO and NH_3 adsorbed on Ni (100) surface.