Resonant Ionic, Covalent Bond, and Steric Characteristics Present in 1Σu+ States of Li2.

The molecular bonding in the excited states of the alkali dimers involves the resonant ionic, covalent bond and steric interactions. We show here the case of the 1Σu+ states of Li2 by ab initio calculation. These interactions as functions of the internuclear distance lead to complex potential energy curves, providing an important application for high resolution laser spectroscopy. The spectroscopic constants for the 4 and 5 1Σu+ states are obtained for the first time.