Abstract
Steric control of chemical reactions on surface is one of the goals for surface scientists. An oriented-molecular beam which we produce utilizing the Stark effect of molecules is a technique to complete such a mission. This technique allows us to select specific rotational quantum states and orientations of the reagent molecules. Thus, we have designed, built and tuned up the UHV-compatible oriented-molecular-beam machine for the elucidation of the reaction dynamics on well defined surfaces. The newly developed machine consists of four differentially pumped chambers. The base pressure was 5 × 10-8 and 1 × 10-8 Pa for the hexapole chamber selecting the quantum state of molecules and the collision chamber for the surface-reaction analysis, respectively. We measured the focusing curve of CH3Cl beam to check the performance of the machine. We could clearly resolve the peaks corresponding to each rotational quantum state. According to the trajectory simulation including the second-order Stark effect, we assign each peak in the focusing curve to the specific rotational state and also estimate the orientational distribution. We achieved a good resolution for the selection of the states with |JKM> = |111> and |212> state.
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