Manipulation of cold molecular ensembles

Speaker: 
Nicolas Vanhaecke
Event Date and Time: 
Thu, 2012-05-31 16:30 - 17:30
Location: 
Chem D215
Local Contact: 
Ed Grant
Intended Audience: 
Graduate

The achievements and prospects opened by atoms in the cold and ultracold regimes cover an impressive range of topics: from precision measurements for fundamental physics, metrology, mesoscopic physics and quantum information to applied physics, such as atomic clocks or ultracold ion beams. Cold molecules are expected to reveal even richer physics than cold atoms, since molecules exhibit a rich rotational and vibrational structure and can also possess additional properties, such as a permanent electric dipole moment or chirality [1]. A prominent, versatile method to produce cold molecules relies on the supersonic expansion of a seeded molecular gas, followed by a deceleration of the molecules of the so-formed beam [2]. In this presentation I will outline the operation principle of the various components which are used in our laboratory to manipulate the motion of the molecules in the beam. The Stark deceleration technique slows down polar molecules with time-dependent electric fields [3], whereas the Zeeman deceleration addresses paramagnetic atoms and molecules [4]. I will also report on the recent, experimental realization of a microwave decelerator for neutral polar molecules, suitable to decelerate and focus molecules in their absolute ground state [5]. In the second part of my talk, I will report on a direct method to accurately measure the density of a Rydberg gas, which we experimentally demonstrate in a supersonic atomic beam. The method gives direct access to the density of the gas, and requires to evaluate neither the atom number nor the volume of the gas. Indeed, two-body information is extracted from measurements that are based on controled dipole-dipole-interactioninduced Landau-Zener transitions in pairs of Rydberg atoms in a time-dependent electric field [6]. The present method could be extended to many Rydberg systems in supersonic beams, but also to ultracold Rydberg samples in the dipole blockade or anti-blockade regimes.

[1] Special issues on Cold Molecules; Eur. Phys. J. D 31, 2004; J. Phys. B: At. Mol. Phys. 39, 2006; New J. Phys. 11, 055049, 2009.

[2] S.Y.T. van de Meerakker, H.L. Bethlem, N. Vanhaecke, and G. Meijer. Manipulation and Control of Molecular Beams, Chemical

Reviews, doi:10.1021/cr200349r, 2012.

[3] H.L. Bethlem, G. Berden, and G. Meijer. Decelerating neutral dipolar molecules. Phys. Rev. Lett. 83, 1558, 1999.

[4] N. Vanhaecke, U. Meier, M. Andrist, B.H. Meier, and F. Merkt. Multistage Zeeman deceleration of hydrogen atoms. Phys. Rev.

A 75, 031402, 2007.

[5] S. Merz, N. Vanhaecke,W. J¨ager, M. Schnell, and G. Meijer. Decelerating molecules with microwave fields. arXiv:1204.4019v1.

[6] N. Saquet, A. Cournol, J. Beugnon, J. Robert, P. Pillet, and N. Vanhaecke. Landau-Zener transitions in frozen pairs of Rydberg

atoms. Phys. Rev. Lett. 104, 133003, 2010.

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