0 Tuning the scattering length on the ground triplet state of Cs

We develop two schemes for tuning the scattering length on the ground triplet state of Cs 2. First, an absolute value of the triplet scattering length of 133 Cs 2 is determined using the experimental data (Fioretti et al, Eur.Phys.J. 5, 389 (1999)). Then, we demonstrate that the large scattering length can be made small and positive by coupling of the 3 Σ + u (6S + 6S) potential to the 3 Π g state by strong off-resonant radiation. A weaker laser field coupling the 3 Σ + u (6S+6S) continuum to the lowest bound level of the excited 3 Σ + g (6S+6P) also can lead to a small positive scattering length. In addition, the scattering length of the 135 Cs isotope is found to be positive. A positive scattering length is a crucial ingredient in obtaining Bose-Einstein condensation from a gas of ultra-cold atoms. This parameter controls the long range repulsion between the atoms and therefore the stability of the process. Manipulating the scattering length will allow to add new candidates to the small list of atomic systems which form a condensate. Schemes to control the scattering length have been suggested based on manipulating the interatomic interactions by external fields. They include the use of a magnetic field to induce a Feshbach resonance [1–7], a use of radio-frequency [8] and dc electric fields [9] and off resonant strong electromagnetic field [10–12]. In the present study we propose two schemes for modification of the scattering length on the ground triplet state of Cs 2