Structure of molecular energy levels of homonuclear diatomic molecules

A new approach is given for the systematic prediction of the low‐lying electronic states of homonuclear diatomic molecules. The approach is based on the bond order and the energy levels of the separated atoms. The asymptotic wave functions are derived from two atomic wave functions by using new operators defined as linear combinations of certain ladder operators. We show that the low angular moment states tend to have a high bond order in the states derived from an asymptote. The observed low‐lying states of C₂, C, Sc₂, and Ti₂ molecules agree with the predictions. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 597–604, 1999