The potential barrier of theB 1Γ u state of Na2

With a semiclassical model the measured energy and width of quasibound levels are described for theB ¹Γ _u state of Na₂. A reliable complete potential function of this electronic state is derived including the potential hump which results from the competition between the electron exchange energy and the long range dipole-dipole interaction. The proposed computation of molecular potentials can be used in the general case and shows some advantages over RKR determinations.