Laser-induced fluorescence to the electronic ground state $\left(X\right)1^1{\Sigma }^{+}$ of LiNa has been recorded by a Fourier-transform spectrometer. Optical excitations of the LiNa molecules into the $\left(A\right)2{}^1{\Sigma }^{+}$ state were performed with different dye lasers. The spectra showed fluorescence progressions up to $v^{\prime \prime }=44$ of the singlet ground state covering 99.9$\%$ of the potential well. However, searches for fluorescence into the triplet ground state $\left(a\right)1{}^3{\Sigma }^{+}$ induced by spin-orbit coupling in the excited system $\left(b\right)1^3\Pi$–$\left(A\right)2{}^1{\Sigma }^{+}$ were not successful. The potential energy curve of the singlet ground state was determined by direct potential fits with a data set of about 8200 assigned lines using two distinct analytical potential representations. In addition, the isotopologue ${}^6\text{Li}{}^{23}\text{Na}$ was studied for a possible need of Born-Oppenheimer corrections by simultaneous fits of both observed isotopologues from ${}^6$Li and ${}^7$Li. Finally, new data on Feshbach resonances from cold-atom experiments at Heidelberg were included for improving the potential description around the dissociation energy for both electronic states $\left(X\right)1{}^1{\Sigma }^{+}$ and $\left(a\right)1{}^3{\Sigma }^{+}$ of the atom-pair ground-state asymptote.

• Received 6 February 2012

DOI:https://doi.org/10.1103/PhysRevA.85.042720