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Generation of cold pulsed molecular beams

University of British Columbia

Methods for understanding and generating pulsed beams of translationally cold molecules through electrostatic velocity filtering are reported. Pulsed beams of acetonitrile (CH₃CN) and calcium monofluoride (⁴⁰Ca¹⁹F) in particular are theoretically examined and experimentally obtained. CH₃CN gas molecules are obtained from the vapour pressure above liquid CH₃CN and introduced to the electrostatic guide through a pulsed nozzle. The observed time of flight indicates a longitudinal velocity of 31 m/s and temperature of 2.37 K. ⁴⁰Ca¹⁹F molecules are obtained through laser ablation off a CaF₂ disk and cooled via buffer gas cooling by a cold pulsed Helium beam prior to being introduced into the electrostatic guide. Longitudinal velocities of 4.47 m/s and temperatures of 70.9 mK are obtained. While results for CH₃CN are within theoretical expectations, results for ⁴⁰Ca¹⁹F are not in agreement with theoretical predictions, indicating either a lack of understanding of the process or a limitation in the current experimental design. Nonetheless, the current experimental apparatus may be used, with minor adjustments to perform depletion spectroscopy on these molecules as well as may be used to generate pulsed beams of other molecules such as barium monofluoride (¹³⁸Ba¹⁹F), which may be used in the determination of the electron's electric dipole moment.

Thesis/Dissertation

application/pdf

2009-05-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/7920

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/