Accurate asymptotic ground state potential curves of Cs\mathsf{_2} from two-colour photoassociation

Over 100 high lying level energies of the lowest electronic states \(X^1{\rm\Sigma}^ + _g\) and \(a^3{\rm\Sigma}^ + _u\) in Cs2 are determined in a \(\Lambda\)-like scheme two-colour photoassociation spectroscopy. The results are analyzed with a coupled channel model using an asymptotic approach, based on nodal lines. From this analysis we determine the long range dispersion coefficient C6 to 6846.2\(\pm\)15.6 a.u. We also obtain the first experimental determination of the amplitude of the asymptotic exchange term.