We have developed the molecu ] ar beam source with non − diaphragm type sma ] 1 shock tube and evaluate the beam characteristics by the time − ofLflight ( TOF ) method . We measureCl TOF distributions ofthe molecular beam ofnitrogen . The shock tUbe with optimized geometry can generate the molecular beam with the translational energy of more than l eV at the repetition rate of O. 5 Hz . The trans] ational energy ofthe beams is contro ] ] ed by the initial pressure ratio . The beam source can

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... o generate dissociated atomic oxygen beam with the fraction ofdissociation control ] ed by the initial pressure ratio , These results demonstrate that our beam source is a promising tool for scattering experiments and surface reaction studies , Key Mords : Molecular beam, Ra τened gas flows , Shock tube, Compressible flows