Gaussian functions in Hylleraas-configuration interaction calculations: Potential curves for the e sup 3. Sigma. sup + sub u and the f sup 3. Sigma. sup + sub u states of hydrogen

The explicitly correlated wave function method (Hylleraas-CI) with Cartesian Gaussian basis sets has been used to calculate the potential curve for the {ital e}{sup 3}{Sigma}{sup +}{sub {ital u}} and {ital f} {sup 3}{Sigma}{sup +}{sub {ital u}} states of the H{sub 2} molecule. Potential barriers of 215 and 10 300 cm{sup {minus}1} are predicted to exist in the {ital e}{sup 3}{Sigma}{sup +}{sub {ital u}} and {ital f} {sup 3}{Sigma}{sup +}{sub {ital u}} states, respectively, and their nature analyzed. Spectroscopic constants for H{sub 2} and D{sub 2} derived from the curves are compared with experiments and other theoretical calculations. It is concluded that the present potential curves are the best theoretical ones to-date and their accuracy is probably as good as the scanty experimental data. No {ital o}{sup 3}{Sigma}{sup +}{sub {ital u}} state below the {ital f} {sup 3}{Sigma}{sup +}{sub {ital u}} state is found in our calculations.