KCS

For all the excited states of a hydrogen molecule up to n = 3 active spaces, potential energy curves (PECs) are obtained for values of the internuclear distance R in the interval [0.5, 10] a.u. within an accuracy of 1 × 10-4 a.u. (Hartree) compared to the accurate PECs of Kolos, Wolniewicz, and their collaborators by using the multi-reference configuration-interaction method and Kaufmann's Rydberg basis functions. It is found that the accuracy of the PECs can be further improved beyond 1 × 10-4 a.u. for that R interval by including the Rydberg basis functions with angular momentum quantum numbers higher than ℓ = 4.