Eur. Phys. J. D 56, 99-104 (2010)
DOI: 10.1140/epjd/e2009-00269-3

Radio-frequency association of molecules: an assisted Feshbach resonance

Q. Beaufils¹, A. Crubellier², T. Zanon¹, B. Laburthe-Tolra¹, É. Maréchal¹, L. Vernac¹ and O. Gorceix<sup>1

1</sup>  Laboratoire de Physique des Lasers, CNRS UMR 7538, Université Paris 13, 99 avenue J.-B. Clément, 93430 Villetaneuse, France
²  Laboratoire Aimé Cotton, CNRS II, Bâtiment 505, Campus d'Orsay, 91405 Orsay Cedex, France

laurent.vernac@univ-paris13.fr

Received 26 June 2009 / Published online 6 November 2009

Abstract
We develop a theoretical model to describe the radio-frequency (rf) induced coupling of a pair of colliding atoms to a Feshbach molecule when a magnetic field arbitrarily far from the Feshbach resonance is modulated in time. We use the dressed atom picture, and show that the coupling strength in presence of rf is equal to the Feshbach coupling strength multiplied by the square of a Bessel function. The argument of this function is equal to the ratio of the atomic rf Rabi frequency to the rf frequency. We experimentally demonstrate this law by measuring the rate of rf-association of molecules using a Feshbach resonance in d wave collisions between ultra-cold chromium atoms.

PACS
34.50.-s - Scattering of atoms and molecules.
67.85.-d - Ultracold gases, trapped gases.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2009