A study of the electron correlations in the H2molecule using the double photoionisation process (γ, 2e)

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Abstract
The differential cross section for the double photoionisation ( gamma , 2e) of the H2 molecule is calculated at the photon energy up to 1 keV bearing in mind the double coincidence experiment. The final electrons are described by plane waves orthogonalised to the electron wavefunction of the H2+ ion at a distance between protons which is equilibrium for the H2 molecule. The differential cross sections are very sensitive to the choice of the wavefunction for the molecular ground state. The interplay of two mechanisms, namely, the 'instantaneous' change in the self-consistent field and a manifestation of the short-range pairwise electron-electron correlations, is discussed. This last mechanism dominates if two final electrons have antiparallel momenta. The experimental problems are outlined; in particular, the (e, 3e) experiment can reveal some essential details of the above mechanisms.