Unusual double-minimum potential energy curves: The h and g3Σ g+ states of the hydrogen molecule

Abstract

Born-Oppenheimer potential energy curves and adiabatic corrections for the h and g 3Σ g + states of the hydrogen molecule have been computed using explicitly correlated wavefunctions in elliptic coordinates. The calculated potential energy curves are more accurate than any previous results for the above states. It is shown that, in contrast to the Born-Oppenheimer results, the adiabatic potential energy curves for the h and g states are characterized by double-minimum functions. The energies of the vibrational levels and rotational constants for both states have been computed. Large differences have been found between theoretical and experimental results. It is, however, possible that the irregular changes of the rotational constant with increasing vibrational excitation, found in the present work, if taken into account, may change the assignment of the experimental term values.