Triplet-singlet conversion in ultracold Cs$_2$ - production of ground state molecules

We present theoretical calculations in molecular cesium for the conversion of ultracold triplet to singlet molecules through the $0_{u}^{+}$ system. We show that strong mixing of $A^{1}\Sigma_{u}^{+} \sim b ^{3}\Pi_{u}$ states facilitates the triplet-singlet conversion. The conversion opens additional channels for enhanced production of deeply bound ultracold molecules in the ground $X$$^{1}\Sigma_{g}^{+}$ state. In addition, our calculations reveal that due to this triplet singlet conversion, the optical pumping and subsequent vibrational cooling can not be applied to the ground triplet $a$$^{3}\Sigma_{u}^{+} $ molecules due in part to this loss mechanism.