Abstract
Using Feshbach's projection operator formalism, the adiabatic potential energies and energy widths of the lowest 1 Sigma u+ and 1 Pi g autoionising states of the H2 molecule are calculated in the region of internuclear distance R from 1.0 to 3.0 au (3.6 au for the 1 Sigma u state). The energy curve and energy width for the 1 Sigma u+ state agree with other calculations. The accuracy of the energy curve and width for the 1 Pi g state is discussed.