Experimental Born–Oppenheimer Potential for theX1Σ+Ground State of HeH+: Comparison with theAb InitioPotential

Abstract

All literature on vibration–rotational and pure rotational transition energies for theX1Σ+state of4HeH+,3HeH+,4HeD+, and3HeD+have been employed in a direct least-squares fit of the radially dependent Hamiltonian. The Born–Oppenheimer potential is represented by a modified Lennard–Jones function that provides for correct behavior in the near dissociation long-range region. Only 19 adjustable parameters were required to represent the 166 measured transition energies, which are reproduced almost to within the measurement accuracies. The fitted potential and Born–Oppenheimer breakdown functions are shown to be in good agreement with the results ofab initiocalculations. The results are used to obtain high-order centrifugal distortion constants as well as level widths for quasi-bound levels.