Method for traveling-wave deceleration of buffer-gas beams of CH

Abstract

Cryogenic buffer-gas beams are a promising method for producing bright sources of cold molecular radicals for cold collision and chemical reaction experiments. In order to use these beams in studies of reactions with controlled collision energies, or in trapping experiments, one needs a method of controlling the forward velocity of the beam. A Stark decelerator can be an effective tool for controlling the mean speed of molecules produced by supersonic jets, but efficient deceleration of buffer-gas beams presents new challenges due to longer pulse lengths. Traveling-wave decelerators are uniquely suited to meet these challenges because of their ability to confine molecules in three dimensions during deceleration and the versatility afforded by the analog control of the electrodes. We have created ground state CH($X^2\Pi$) radicals in a cryogenic buffer-gas cell with the potential to produce a cold molecular beam of $10^{11}$ mol./pulse. We present a general protocol for Stark deceleration of beams with large position and velocity spreads for use with a traveling-wave decelerator. Our method involves confining molecules transversely with a hexapole for an optimized distance before deceleration. This rotates the phase-space distribution of the molecular packet so that the packet is matched to the time varying phase-space acceptance of the decelerator. We demonstrate with simulations that this method can decelerate a significant fraction of the molecules in successive wells of a traveling-wave decelerator to produce energy-tuned beams for cold and controlled molecule experiments.

8 pages, 7 figures

References in corpus (3)

• A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules
• Magnetic Trapping of Molecules via Optical Loading and Magnetic Slowing
• Static trapping of polar molecules in a traveling wave decelerator

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• Quantum-State-Specific Reaction Rate Measurements for the Photo-induced Reaction Ca${}^{+}$ + O${}_2$ $\to$ CaO${}^{+}$ + O
• Beyond the Limits of Conventional Stark Deceleration
• Shaped nozzles for cryogenic buffer gas beam sources
• Electrostatic guiding of the methylidyne radical at cryogenic temperatures