Calculation of the interspecies s-wave scattering length in an ultracold Na-Rb vapor

We report the calculation of the interspecies scattering length for the sodium-rubidium (Na-Rb) system. We present improved hybrid potentials for the singlet $X^1\Sigma {}^{+}$ and triplet $a^3{\Sigma }^{+}$ ground states of the NaRb molecule, and calculate the singlet and triplet scattering lengths $a_s$ and $a_t$ for the isotopomers ${}^{23}{\mathrm{Na}}^{87}\mathrm{Rb}$ and ${}^{23}{\mathrm{Na}}^{85}\mathrm{Rb}.$ Using these values, we assess the prospects for producing a stable two-species Bose-Einstein condensate in the Na-Rb system.