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A pulsed superthermal beam source for metastable atomic and molecular species

Describes the construction and characterisation of a pulsed, superthermal molecular beam source incorporating a rotor accelerator and a synchronously pulsed electron bombarder. The addition of the pulsed bombarder greatly improves the kinetic energy resolution of the superthermal metastable atomic and molecular beams, particularly for light particles at low velocities and eliminates problems of 'wrap-around' at low velocities. The optimum conditions of resolution at a desired signal level are discussed: a typical velocity distribution for Ar(3P2) at a most probable beam velocity of 1500 m s-1 would have a standard deviation sigma approximately=0.07.