Abstract
A novel type of electrostatic state selector for molecules has been devised which has a high transparency to rejected molecules and permits focusing of molecules with mu eff<0. The electrode geometry is that of a single-wire helix placed concentrically within a coaxial outer electrode, which may be the vacuum chamber itself. Theoretical analysis of the electrostatic potential within the helix reveals that the device has the characteristics of a 'leaky' potential well for a molecular beam passing through it. An optimal electrode geometry of a helix pitch three to four times the helix radius is calculated. Experimental results are obtained for the unifilar helix focuser in a molecular beam maser oscillator and spectrometer, the latter being used as a beam detector. Whilst the state selector in its present form appears to have state selection properties somewhat inferior to existing electrostatic focusers, it is unique in respect of its simplicity of construction.
Published Version
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