Feshbach resonances in Cesium at Ultra-low Static Magnetic Fields

D. J. Papoular 1, 2, S. Bize 3, A. Clairon 3, H. Marion 3, S. J. Kokkelmans 4, G. V. Shlyapnikov 1, 5

Physical Review A 86 (2012) 040701

We have observed Feshbach resonances for 133Cs atoms in two different hyperfine states at ultra-low static magnetic fields by using an atomic fountain clock. The extreme sensitivity of our setup allows for high signal-to-noise-ratio observations at densities of only 2*10^7 cm^{-3}. We have reproduced these resonances using coupled-channels calculations which are in excellent agreement with our measurements. We justify that these are s-wave resonances involving weakly-bound states of the triplet molecular Hamiltonian, identify the resonant closed channels, and explain the observed multi-peak structure. We also describe a model which precisely accounts for the collisional processes in the fountain and which explains the asymmetric shape of the observed Feshbach resonances in the regime where the kinetic energy dominates over the coupling strength.

  • 1. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
    CNRS : UMR8626 – Université Paris XI - Paris Sud
  • 2. Dipartimento di Fisica,
    Universita Trento
  • 3. Systèmes de Référence Temps Espace (SYRTE),
    CNRS : UMR8630 – INSU – Observatoire de Paris – Université Paris VI - Pierre et Marie Curie
  • 4. Department of Physics,
    Eindhoven University of Technology
  • 5. Van der Waals-Zeeman Institute,
    University of Amsterdam