Single-Center Calculations on the Lowest-Lying Πu and Πg Excited States of H2

Single-center wavefunctions are constructed for the lowest-lying singlet and triplet Πu(1sσ2pπ) and Πg(1sσ3dπ) excited states of the hydrogen molecule using a basis set of integral Slater-type orbitals centered at the molecular midpoint. It is found that the convergence is more rapid than for a corresponding single-center calculation on the ground state. The error in the binding energy is about 0.065 eV for the Πu states and 0.033 eV for the Πg states if a 19-term configuration-interaction wavefunction is used for the description of each.