High resolution photoassociation spectroscopy of the excited c3Σ1+ potential of Na23Cs133

We report on photoassociation spectroscopy probing the $c^3{\mathrm{\Sigma }}_1^{+}$ potential of the bialkali NaCs molecule, identifying 11 vibrational lines between $v^{\prime }=0$ and $v^{\prime }=25$ of the excited $c^3{\mathrm{\Sigma }}_1^{+}$ potential and fitting their rotational and hyperfine structure. The observed lines are assigned by fitting to an effective Hamiltonian model of the excited-state structure with rotational and hyperfine constants as free parameters. We discuss unexpected broadening of select vibrational lines and its possible link to strong spin-orbit coupling of the $c^3{\mathrm{\Sigma }}_1^{+}$ potential with the nearby $b^3{\mathrm{\Pi }}_1$ and $B^1{\mathrm{\Pi }}_1$ manifolds. Finally, we report use of the $v^{\prime }=22$ line as an intermediate state for two-photon transfer of weakly bound Feshbach molecules to the rovibrational ground state of the $X^1{\mathrm{\Sigma }}^{+}$ manifold.