Fritz-Haber-Institut der Max-Planck-Gesellschaft

Abteilung Molekülphysik


Development of manipulation and trapping elements for polar molecules

An AC-trap For Polar Molecules

Polar molecules in low-field seeking states can be trapped at the minimum of a electric field. A maximum of the electric field in free space, which would allow trapping of molecules in high-field seeking states, is not allowed by Maxwell's equations. It is, on the other hand, possible to create a cylindrically symmetric geometry having a maximum in the radial direction and a minimum in the axial direction, or vice versa. Switching between these two saddle point configurations results in a field that confines molecules in both low-field and high-field seeking states.

A Molecular Synchrotron

Rather than trapping particles in a trap, as is common in atomic physics, particles can also be stored in rings. We have developed a synchrotron for low-energy neutral molecules composed of two hexapole half-rings separated by a gap. Every time the molecules pass through the gap, the electric fields are switched such as to accelerate or decelerate, and focus the molecules in the longitudinal direction.

A Molecular Fountain

Ultimately the resolution of any measurement is limited by the time a molecule spends in the measuring device. In collaboration with the Laser Centre Vrije Universiteit in Amsterdam, a molecular fountain is being set up. In this device a beam of molecules is decelerated and cooled using switched electric fields and subsequently directed upwards. The molecules will fly upwards some 30 cm before falling back under gravity, thereby passing a microwave cavity twice; as they move up and down. In this way the effective interrogation time is half a second, allowing for a very high accuracy.

other experiments in the Molecular Physics group

Members of the Group



Phone /Institution

Rick Bethlem

Group Leader 0049-30-8413 5741 / FHI
0031-20-598 7951 /VU
Cynthia Heiner PhD Student 0049-30-8413 5731 / FHI
Jacqueline van
PhD Student 0049-30-8413 5732 / FHI

Former Group Members



David Carty Physical and Theoretical Chemistry Laboratory, Oxford, United Kingdom
Floris Crompvoets Philips Electronics Netherlands




Phone /Institution
Melanie Schnell PostDoc 0049-30-8413 5604 / FHI


Laser Centre Vrije Universiteit

Rick Bethlem's homepage at VUAmsterdam

FOM-Institute for Plasma Physics

Recent Publications

Bethlem, H. L., M. Kajita, B. Sartakow, G. Meijer and W. Ubachs,
Prospects for precision measurements on ammonia molecules in a fountain.
The European Physical Journal Special Topics 163, 55-69 (2008).

Heiner, C. E., G. Meijer and H. L. Bethlem,
Motional resonances in a molecular synchrotron.
Physical Review A 78, 030702-1-032707-4 (2008).

Meerakker, S. Y. T. v. d., H. L. Bethlem and G. Meijer,
Taming molecular beams.
Nature Physics, 4, 595-602 (2008).

Schnell, M., P. Lützow, J. van Veldhoven, H. L. Bethlem, J. Küpper, B. Friedrich, M. Schleier-Smith, H. Haak and G. Meijer
A Linear AC Trap for Polar Molecules in Their Ground State.
The Journal of Physical Chemistry A 111, 31, 7411-7419 (2007).

Heiner, C. E., D. Carty, G. Meijer and H. L. Bethlem
A Molecular Synchrotron
Nature Physics 3, 115-118 (2007).

Bethlem, H. L., J. van Veldhoven, M. Schnell and G. Meijer
Trapping polar molecules in an ac trap
Physical Review A, 74, 063403-1- 063403-15 (2006).

Bethlem, H. L., M. R. Tarbutt, J. Küpper, D. Carty, K. Wohlfart, E. A. Hinds and G. Meijer
Alternating gradient focusing and deceleration of polar molecules.
Journal of Physics B 39, R263-R291 (2006)

Heiner, C. E., H. L. Bethlem and G. Meijer
Molecular beams with a tunable velocity.
Physical Chemistry Chemical Physics, 8, 23, 2666-2676 (2006).

Veldhoven, J. van, H. L. Bethlem, M. Schnell and G. Meijer
Versatile electrostatic trap.
Physical Review A, 73, 063408-1-063408-7 (2006).

Meerakker, S. Y. T. van de, N. Vanhaecke., H. L. Bethlem and G. Meijer
Transverse stability in a Stark decelerator.
Physical Review A 73, 023401-1-023401-13 (2006).

Crompvoets, F. M. H., H. L. Bethlem and G. Meijer
A storage ring for neutral molecules.
Advances in Atomic, Molecular, and Optical Physics 52. (Eds.) Paul R. Berman, Chun D. Lin. Elsevier Academic Press, Amsterdam (2006) 209-287.

Meerakker, S. Y. T. van de, N. Vanhaecke, H. L. Bethlem and G. Meijer
Higher-order resonances in a Stark decelerator
Physical Review A 71,053409 (14 pages) (2005) .

Veldhoven, J. van, H. L. Bethlem and G. Meijer
ac Electric trap for ground-state molecules
Physical Review Letters 94, 083001 (4 pages) (2005).

Schulz, S. A., H. L. Bethlem, J. van Veldhoven, J. Küpper, H. Conrad and G. Meijer
Microstructured Switchable Mirror for Polar Molecules.
Physical Review Letters 93, 2, 020406-1-4 (2004).

Veldhoven, J. van, J. Küpper, H. L. Bethlem, B. Sartakov, A. J. A. van Roij and G. Meijer
Decelerated molecular beams for high-resolution spectroscopy: the hyperfime structure of 15ND3.
The European Physical Journal D 31, 2, 337-349 (2004).

Tarbutt, M.R., H.L. Bethlem, J.J. Hudson, V.L. Ryabov, V.A. Ryzhov, B.E. Sauer, G. Meijer and E. A. Hinds
Slowing heavy, ground-state molecules using an alternating gradient decelerator.
Physical Review Letters 92, 17, 173002-1-4 (2004).

Crompvoets, F. M. H., H. L. Bethlem, J. Küpper, A. J. A. van Roij and G. Meijer
Dynamics of neutral molecules stored in a ring.
Physical Review A 69, 063406-1-5 (2004).


Veldhoven, J. van
AC trapping and high-resolution spectroscopy of ammonia molecules
Radboud Universiteit Nijmegen (2006)

Crompvoets, F. M. H
A Storage Ring for Neutral Molecules
Radboud Universiteit Nijmegen (2004)

Bethlem, H. L.
Deceleration and trapping polar molecules using time-varying electric fields
Katholieke Universiteit Nijmegen (2002)

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