Gaussian functions in Hylleraas‐configuration interaction calculations: Potential curves for the e 3∑+u and the f 3∑+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 e3∑+u and f 3∑+u states of the H2 molecule. Potential barriers of 215 and 10 300 cm−1 are predicted to exist in the e3∑+u and f 3∑+u states, respectively, and their nature analyzed. Spectroscopic constants for H2 and D2 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 o3∑+u state below the f 3∑+u state is found in our calculations.