The Li2F (1)Sigma(+)(g) "shelf" state: Accurate potential energy curve based on the inverted perturbation approach

We report an accurate inverted perturbation approach (IPA) potential energy curve for the "shelf" F (1)Sigma (+)(g) state in Li-2 which reproduces pos itions of the experimental energy levels available in the literature for al l three isotopomers Li-7(2), (LiLi)-Li-6-Li-7, and Li-6(2) with a standard deviation of 0.11 cm(-1). Our analysis significantly improves the shape of the recently reported Rydberg-Klein-Rees (RKR) potential curve of the F (1) Sigma (+)(g) state [Antonova , J. Chem. Phys. 112, 7080 (2000)] and provide s evidence for the existence of a shallow minimum in the shelf region. Usin g our IPA potential curve we were able to localize and identify some local perturbations in the spectra, as well as to correct the assignment of sever al spectral lines previously observed experimentally. (C) 2000 American Ins titute of Physics. [S0021-9606(00)31040-6].