UBC Theses and Dissertations

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UBC Theses and Dissertations

Manipulation of the motion of polyatomic molecules by AC and DC Stark deceleration Nourbakhsh, Omid


A conventional DC Stark decelerator, consisting of 180 stages, was constructed and tested. The experimental setup was characterized using ammonia (NH₃) as the reference molecule. Resonance Enhanced Multi-Photon Ionization method (REMPI) was used to detect the ammonia molecules. Deceleration of ammonia molecules was observed and improved by optimizing the design and simulations. Bunching of the molecules with the decelerator electrodes was implemented to improve the signal. The design was optimized by removing the hexapole which was between the nozzle and the decelerator, and also by reducing the distance between the detection point and the decelerator. Finally, deceleration of ammonia molecules from 425 m/s to 27.9 m/s (~1.5 K) was demonstrated. Sulphur deuteride (𝑆𝐷 radical) as a new sample was decelerated. Laser Induced Fluorescence (LIF) of the excited 𝑆𝐷 radicals was collected as the detection method. Deceleration of 𝑆𝐷 radicals in the | X²Π₃/β‚‚,Ξ½=0,J=3/2,Mj=-3/2βŒͺ energy state from 440 m/s to 301 m/s, and deceleration of 𝑆𝐷 radicals in the | X²Π₃/β‚‚,Ξ½=0,J=5/2,Mj=-5/2βŒͺ energy state from 440 m/s to 415 m/s was obtained. A deceleration scheme was presented to obtain separate and sate purified decelerated packets of SD radicals in J=3/2 and J=5/2. The Cavity Enhanced Laser Induced Fluorescence (CELIF) method for measuring the absolute density of the Stark decelerated molecular packets was explained, and the first steps toward its implementation were taken. In parallel with the DC Stark decelerator a prototype superconducting microwave cavity was designed, constructed, and characterized to be used for future AC Stark deceleration experiments. An electrochemical plating method was used to coat the copper microwave cavity with a lead-tin (Pb-Sn) alloy. An unloaded quality factor of 10⁢ was obtained for the superconducting cavity. The possibility of deceleration with the superconducting cavity is discussed.

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