THE A(3)SIGMA(+)(G) STATE OF THE HYDROGEN MOLECULE

The Born-Oppenheimer potential energy curve and the adiabatic correcti ons for the a(3) Sigma(g)(+) state of the hydrogen molecule have been recalculated for a wide range of internuclear distance using explicitl y correlated wavefunctions in elliptic coordinates. The calculated pot ential energy curve is lower than the previous one by more than I cm(- 1). The energies of the vibrational levels and rotational constants fo r this state have been also computed. In addition, the nonadiabatic co rrections have been estimated on the basis of an approximate Van Vleck formula. The estimated nonadiabatic shift for the lowest level of H-2 has been independently confirmed by comparing the nonadiabatic energy calculated by Bishop and Cheung with the adiabatic energy presented i n this work. It is shown that by taking into account estimated nonadia batic corrections as well as relativistic and radiative effects, excel lent agreement with experiment is achieved. (C) 1995 Academic Press, I nc.