The Nature of Bonding in Diatomic Noble Gas Ions

If one electron is removed to yield He2, the equilibrium distance between the two He nuclei decreases to 1.08 A. This is caused by the contraction of the 

There is a MEP path connecting the two nuclei of He2 The electron density p at the (3, — 1). critical point, the midpoint between the two He atoms, is 

which is typical of a covalent bond. More convincing is the result that  

If a second electron is removed as in Hel, the internuclear distance decreased to 0.70 A for the same reasons described for He2 The electron density at the (3, - 1) critical point is 4.4 e/A, while the energy density Hg is - 4.4 hartree/A, both indicating covalent bonding. 

Nevertheless, covalent bonding between He and X is possible for the monocations HeX . It requires a rearrangement of electrons in the valence shell of X thus yielding an excited electronic state of X and, subsequently, HeX . The electron rearrangement must be such that the electron acceptor ability of 

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