Double-Minimum Potential Energy Curves Resulting from Adiabatic Effects: The 4s3Σ+gand 4d3Σ+gStates of the Hydrogen Molecule

Abstract

The Born–Oppenheimer potential energy curve and the adiabatic corrections for the 4sand 4d3Σ+gstates of the hydrogen molecule have been calculated for a wide range of internuclear distance using explicitly correlated wavefunctions in elliptic coordinates. It is shown that similarly to the 4sstate the 4dalso state exhibits a single-minimum potential energy curve in the BO approximation and a double-minimum potential energy curve in the adiabatic approximation. The energies of the vibrational levels and rotational constants for both states have been computed. As a result of the existence of the double-minimum potential energy curves, the sets of vibrational levels form two series of levels, each connecting with outer or inner minimum. Large and irregular discrepancies with experimental data have been found. This is partially a consequence of not applying the nonadiabatic corrections, which are expected to play an important role in this case.