Accurate studies on the full vibrational energy spectra and molecular dissociation energies for some electronic states of the Li2 molecule

It is usually very difficult to directly obtain molecular dissociation energy D_e and all accurate high-lying vibrational energies for most diatomic electronic states using modern experimental techniques or quantum theories, and it is also very difficult to give accurate analytical expression for diatomic molecular dissociation energy. This study proposes a new analytical formula for obtaining accurate molecular dissociation energy based on the LeRoy and Bernstein's energy expression in dissociation limit. A set of full vibrational energy spectra for some electronic states of Li₂ molecule are studied using the algebraic method (AM) suggested recently, and the corresponding accurate molecular dissociation energies are evaluated using the proposed new formula and high-lying AM vibrational energies. The results show that the AM spectra and the new theoretical dissociation energies agree very well with experimental data, and thereby providing a new physical approach to generating accurate dissociation energies for electronic states of diatomic molecules.