ANALYTICAL POTENTIAL-ENERGY CURVES OF INVERSE POLYNOMIAL FORM FOR DIATOMIC-MOLECULES - AN APPLICATION OF 2-STEP METHOD TO LI-2, NA-2, NAK, AND K-2 MOLECULES

We apply the recently introduced two-step method to the lowest triplet electronic states of the diatomic molecules Li-2, Na-2, NaK, and K-2. The analytical potential energy curves of these states are constructe d in the form of inverse polynomial with the experimental vibrational energies as the only inputs. The dissociation energies and the equilib rium constants are also determined. The forms of the interatomic poten tials have correct asymptotic behavior in both the short range limit a nd the long range limit. In contrast to the situations in the widely-u sed RKR method and also the Dunham type potentials, none of the unphys ical inner and outer walls appears in our interatomic potential curves . Based on the potentials obtained, it is predicted that additional un observed higher vibrational bound states exist for all the systems con sidered here. This is to be compared with the fact that both the RKR m ethod and the Dunham type potentials have so far failed to predict the existence of the additional bound states for these systems. The descr ibed treatments can be applied to other systems as well.