Honors Program


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Brunner, W. J. (2021). Study of neon collisional negative ion compound resonance using a trochoidal electron monochromator. Undergraduate Honors Thesis. University of Nebraska-Lincoln.


Copyright Will Brunner 2021.


This thesis describes the experimental apparatus and procedure used to measure the excitation function of the 2p53p 3D3 state of neon. First I describe the effect on this excitation of negative ion resonances and previous experiments to measure the excitation function, as well as suggestions for future applications of such studies. Then the experimental apparatus is described in three parts. The vacuum system uses a turbomolecular pump to decrease the pressure of the chamber to as low as 4*10-9 Torr. The electron beam system incorporates a trochoidal electron monochromator to send a highly monochromatic beam of electrons (wide) into the neon collision cell, which allows for better resolution of the resonant features in the excitation function that could be obtained by a standard thermionically emitted electron beam. The installation of a new barium oxide cathode electron source is discussed, which has advantages over the tungsten filament used previously, particularly with regard to reduction in background light. The light analysis system can measure the intensity of light emitted from the collision cell, and employs a polarimeter to measure the Stokes parameters of the emitted light. Improvements to the apparatus made this year include the resolution of an inconsistency in angle measurement for polarimeter measurements. The utility of the ion optics program SIMION® is also considered, which can model the electron beam system to optimize its use. Finally, the method for measuring the excitation function is explained in detail.