First observation of feshbach resonances at very low magnetic field in a   133Cs fountain
  One of the main limitations of cesium atomic fountains has been the cold collision frequency shift. By using a method based on a transfer of population by adiabatic passage allowing to prepare cold atomic samples with a well defined ratio of atomic density as well as atom number the collisional shift is controlled at the 10E-3 of its value. A calibration of Zeeman sub-states contribution to the clock shift as a function of the field has been performed. Feshbach resonances have been observed for the first time at very low magnetic field and with a very good resolution. A Monte Carlo simulation has been performed and could fit properly some of experimental data. This constrains some parameters of the theory of collisions. 
H. Marion (SYRTE), S. Bize (SYRTE), L. Cacciapuoti (SYRTE), D. Chambon   (SYRTE), F. Pereira Dos Santos (SYRTE), G. Santarel...