The Heitler-London Repulsive State of Hydrogen

Abstract

A variational method has been used in the study of the 1sσ2pσ 3 Σ u state of H2. Two independent computations with formally different functions gave, for a nuclear separation of 1.5a H, energies which agreed to within 0.03 ev and functions with a root‐mean‐square fractional difference of about 2 percent. A study of the way in which the computed energies converged to a limit, as the complexity of the varied functions was increased, indicates that the interaction energy of the atoms at this distance is +5.145±0.02 ev. Computations were also made for nuclear separations of 1.6 a H and 1.87 a H. A potential curve passed through points thus determined and approaching the Heitler‐London curve asymptotically for large nuclear separations is believed to be accurate to 0.2 ev for nuclear separations greater than 1.35 a H. This curve is compared with the results of previous computations and the curve constructed by Finkelnburg and Weizel to account for the variation with wave‐length of the excitation potential of the continuous spectrum. Discussion of the disagreement with the results of Finkelnburg and Weizel is deferred to a later paper.