  The Deng-Fan potential is used to discuss the reliability of the improved
Greene-Aldrich approximation and the factorization recipe of Badawi et al.'s
[17] for the central attractive/repulsive core. The factorization recipe is
shown to be a more reliable approximation and is used to obtain the
ro-vibrational energies for the lithium dimer. For each vibrational state only
a limited number of the rotational levels are found to be supported by the
lithium dimer.
