High orbital angular momentum states in H2 and D2. III. Singlet–triplet splittings, energy levels, and ionization potentials

Abstract
The 5g–4 fRydberg groups of H2 and D2 first studied in paper I have been obtained with a tenfold increase in resolution which made it possible to resolve the singlet from the triplet components. As a result we can now establish separately precise values for the energy levels in the triplet and singlet systems. For this purpose we have remeasured a number of transitions between the lower energy levels for which at present only old measurements are available. In particular we obtain accurate values for the energies of the lowest (stable) triplet state a 3Σ+ g relative to the singlet ground state, as well as of the ionization potential. The values obtained for the former are more accurate than obtained from singlet–triplet anticrossings while the latter are of similar accuracy as those reported recently by McCormack e t a l. [Phys. Rev. A 3 9, 2260 (1989)] and fit well within this accuracy with the most recent a b i n i t i o values.