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arXiv:0809.1728 · Physical Review A

Cold guided beams of water isotopologs

M. Motsch, L. D. van Buuren, Christian Sommer, Martin Zeppenfeld, Gerhard Rempe, Pepijn W. H. Pinkse

Published Jan 7, 2009• 30 citations
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Abstract

Electrostatic velocity filtering and guiding is an established technique to produce high fluxes of cold polar molecules. In this paper we clarify different aspects of this technique by comparing experiments to detailed calculations. In the experiment, we produce cold guided beams of the three water isotopologs ${\mathrm{H}}_{2}\mathrm{O}$, ${\mathrm{D}}_{2}\mathrm{O}$, and HDO. Their different rotational constants and orientations of electric dipole moments lead to remarkably different Stark shift properties, despite the molecules being very similar in a chemical sense. Therefore, the signals of the guided water isotopologs differ on an absolute scale and also exhibit characteristic electrode voltage dependencies. We find excellent agreement between the relative guided fractions and voltage dependencies of the investigated isotopologs and predictions made by our theoretical model of electrostatic velocity filtering.

DOI
10.1103/physreva.79.013405

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High fluxes of cold polar molecules are efficiently produced by electric guiding and velocity filtering. Here, we investigate different aspects of the beam formation. Variations of the source parameters such as density and temperature result in characteristic changes in the guided beam. These are observed in the velocity distribution of the guided molecules as well as in the dependence of the signal of guided molecules on the trapping electric field. A model taking into account velocity-dependent collisional losses of cold molecules in the region close to the nozzle accurately reproduces this behaviour. This clarifies an open question on the parameter dependence of the detected signal and gives a more detailed understanding of the velocity-filtering and guiding process.
We demonstrate electrostatic guiding of cold heavy water (D(2)O) molecules over a distance of 44.5 cm by using a quadrupolelike electrostatic field, which is generated by the combination of two parallel charged poles and two grounded metal plates. We measure the transverse spatial distribution of the guided D(2)O molecular beam and study the dependence of the relative guiding efficiency and the transverse temperature of the guided molecular beam on the guiding voltage. Our study shows that the maximum guiding efficiency of approximately 50% can be obtained, and our experimental results are in good agreement with ones of theoretical calculation and Monte Carlo simulations, and this guiding scheme has some potential applications in molecule optics, such as molecular-beam splitter, integrated molecular optics, etc.
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