Hyperthermal molecular beam source using a non-diaphragm-type small shock tube

We have developed a hyperthermal molecular beamsource employing a non-diaphragm-type smallshock tube for gas –surface interaction studies. Unlike conventional shock-heated beamsources, the capability of repetitive beam generation without the need for replacing a diaphragm makes our beamsource suitable for scattering experiments, which require signal accumulation for a large number of beam pulses. The short duration ofshock heating alleviates the usual temperature limit due to the nozzle material, enabling the generation of a molecular beam with higher translationalenergy or that containing dissociated species. The shock-heated beam is substantially free from surface-contaminating impurities that are pronounced in arc-heated beams. We characterize the properties of nitrogen and oxygen molecular beams using thetime-of-flight method. When both the timing of beam extraction and the supply quantity of nitrogen gas are appropriately regulated, our beamsource can generate a nitrogen molecular beam with translationalenergy of approximately 1 eV, which corresponds to the typical activationenergy of surface reactions. Furthermore, our beamsource can generate an oxygen molecular beam containing dissociated oxygen atoms, which can be a useful probe for surface oxidation. Thedissociation fraction along with the translationalenergy can be adjusted through the supply quantity of oxygen gas.

Source: Review of Scientific Instruments - October 13, 2016 Category: Physics Authors: Yuta Yoshimoto, Kenichi Osuka, Nobuya Miyoshi, Ikuya Kinefuchi, Shu Takagi and Yoichiro Matsumoto Source Type: research