Highly Excitedς−states of Molecular Hydrogen

We report calculations of H-2 Sigma(-) states using a variational R-matrix approach combined with multichannel quantum defect theory. Several Rydberg series converging to the 2p pi state of the H-2(+) ion core are established and their mutual channel interactions characterized. The influence of the external electron on the chemical bond is found to be particularly strong in these electronically and chemically weakly bound states.