Electronic States of the C2 Radical

LCAO MO’s and ionization energies have been calculated for the 3Σ9− KK′ (1σg)2(1σu)2(1πu)2(2σg)2 and 1Σg+KK′(1σg)2(1σu)2(1πu)4 state of the C2 radical at the internuclear distance of 1.33 Å using the LCAO-SCF method. The interactions of all the electrons have been taken into consideration, but the orthogonality relationship between the Is and the other orbitals was assumed. The LCAO MO’s obtained are in good agreement with those predicted by Mulliken. Using these LCAO MO’s, the lower electronic states have been investigated without configuration interaction. The calculated levels are generally in good agreement with the experimental. The ground state obtained is the 3Σg− state, while the observed is the 3IIu, but the result is not conclusive because of the ignorance of the inner-shell-outer-shell-mixing.