ClF diatomic molecule: Rovibrational spectra

Following the first principles the analytic Born-Oppenheimer (BO) potential curve for the ground state X1 sigma+ of the molecule ClF is proposed for whole range of internuclear distances R is an element of [0, infinity). 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 <= 10(-4) hartree. The van der Waals constant C-6((ClF)) similar to 29.3 a.u. is predicted.