The electron beam fluorescence method as applied to molecular scattering experiments

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Abstract
A molecular beam system using electron beam excitation to observe the rotational state distribution of incident and scatteredbeams of nitrogen is described. The incident nitrogen beam is skimmed from a nozzle source and has low translational and rotational temperatures. Cryopumping of the scattering chamber is necessary to maintain a sufficiently low partial pressure of wall scattered nitrogen in the detection region. The electron gun is of special design for attaining (typically) 15 mA at 1200 eV energy in a millimeter diameter beam. Recording instrumentation is of analog type, the signal to noise ratio of a scatteredbeam is typically of order 40 using a 5 sec integration time constant. The system has been used to infer the anisotropy of nitrogen‐rare gas intermolecular potentials.