ClF diatomic molecule: rovibrational spectra

Following the first principles the analytic Born-Oppenheimer (BO) potential curve for the ground state $X^1\Sigma^+$ of the molecule ClF is proposed for whole range of internuclear distances $R \in [0,\infty)$. It is based on matching the perturbation theory at small internuclear distances $R$ and multipole expansion at large distances $R$, it has the form of two-point Pade approximant and provides 3-4 figures in rovibrational energies. It supports 5719 rovibrational states with maximal vibrational number $\nu_{max} = 47$ and maximal angular momentum $L_{max} = 210$ including 36 weakly-bound states close to threshold (to dissociation limit) with the energies $\lesssim 10^{-4}$ Hartree. The van der Waals constant $C^{(ClF)}_6\ \sim\ 29.3$ a.u. is predicted.