Electronic structure of C₂

The electronic structure of the C2 molecule has been studied over the range R= 1.5a0 to 8.0a0 using three different Slater-type-orbital basis sets and two different levels of configuration interaction. Analytic potential curves and computed spectroscopic constants are given for all states studied. The behavior of all eigenvalues of each CI matrix was studied extensively with excellent agreement between molecular results and those obtained by independent calculations on a pair of separated carbon atoms. The Wigner-Witmer rules were obeyed in every case. Observed and computed spectroscopic constants were highly correlated statistically; linear relationships were determined which allow semiempirical prediction of spectroscopic constants for those states not yet observed. Using the predictions for Τ6, an electronic spectrum has been derived.