Trapping polar molecules in an ac trap

Hendrick L. Bethlem, Jacqueline van Veldhoven, Melanie Schnell, and Gerard Meijer
Phys. Rev. A 74, 063403 – Published 5 December 2006

Abstract

Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell’s equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of ND315 ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270mm3(ms)3 remain trapped. This corresponds to a trap depth of about 5mK and a trap volume of about 20mm3.

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  • Received 29 September 2006

DOI:https://doi.org/10.1103/PhysRevA.74.063403

©2006 American Physical Society

Authors & Affiliations

Hendrick L. Bethlem1,2,*, Jacqueline van Veldhoven1,3, Melanie Schnell1, and Gerard Meijer1

  • 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
  • 2Laser Centre Vrije Universiteit, De Boelelaan 1081, NL-1081HV Amsterdam, The Netherlands
  • 3FOM-Institute for Plasmaphysics Rijnhuizen, P.O. Box 1207, NL-3430 BE Nieuwegein, The Netherlands

  • *Electronic address: rick@fhi-berlin.mpg.de

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Issue

Vol. 74, Iss. 6 — December 2006

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