A VB calculation for the excited bound state of the H2 molecule

It is shown in this Letter that the erroneous bond length resulting for the bound 1 Σ u + state of H2 described by the ionic valence bond structure over the minimum set of 1s STO functions is corrected by the variational inclusion with a substantial weight of the singly excited covalent structures involving 2s and 2pσ STOs onto each H atom. The corresponding value for the molecular energy resulting from the complete optimization of the orbital exponents gives now over 96% of the accurate Kołos–Wolniewicz results.