Abstract
The Hylleraas‐CI method with Cartesian Gaussian basis functions has been used to calculate the potential energy curve of the repulsive b 3+u state of the hydrogen molecule at internuclear distances R ranging from 1.0 to 12.0 bohrs. At small R, sizable improvements over the best previous calculations using elliptical coordinates are reported. The potential curve for the bound e 3+u state is also reported, as a by‐product since it compares very well with the best conventional CI results.