Theoretical study of autoionising states of molecules; H₂and He₂²⁺

The adiabatic potential energy curves of the lowest 1 Sigma g + , 1 Pi g , and 1 Delta g autoionising states for H 2 are obtained in the region of internuclear distance 1.0<or=R<or=5.0 au, using Feshbach's projection operator techniques. The energy shift and the energy width of the lowest 1 Sigma g + autoionising state are calculated for 1.0<or=R<or=2.6 au. It is found that near the stabilisation point (R=2.53 au), the shift is considerable and its effect on the width is not negligible. The revised results for He 2 2+ are also presented.