Europhys. Lett.
Volume 73, Number 6, March 2006
Page(s) 839 - 845
Section The physics of elementary particles and fields
Published online 08 February 2006
Europhys. Lett., 73 (6), pp. 839-845 (2006)
DOI: 10.1209/epl/i2005-10477-3

Measurement of the van der Waals force using reflection of cold atoms from magnetic thin-film atom mirrors

A. K. Mohapatra and C. S. Unnikrishnan

Fundamental Interactions Lab (Gravitation Group) Tata Institute of Fundamental Research Homi Bhabha Road, Mumbai-400 005, India

received 23 September 2005; accepted in final form 24 January 2006
published online 8 February 2006

We report on a measurement of the van der Waals interaction between rubidium atoms in the ground state and a metallic surface, employing a new method involving reflection of laser-cooled atoms from magnetic thin-film atom mirrors. We made use of the fact that the typical distance from which atoms reflect from thin-film magnetic mirrors is of the order of the magnetic domain size and the thickness of the thin film. The modification of the reflectivity of cold atoms from cobalt thin-film magnetic mirrors, with thickness in the range of $200\mbox{--}20\un{nm}$, due to the competition between the attractive atom-surface interaction and the repulsive magnetic interaction enabled the measurement of the van der Waals force in the range 20-$50\un{nm}$ with an uncertainty of 15%. The measured value agrees well with recent theoretical estimates.

34.50.Dy - Interaction of atoms and molecules with surfaces; photon and electron emission; neutralization of ions.
03.75.Be - Atom and neutron optics.
32.80.Pj - Optical cooling of atoms; trapping.

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