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We extend our approach of asymptotic parametrix construction for Hamiltonianoperators from conical to edge-type singularities which is applicable tocoalescence points of two particles of the helium atom and related two electronsystems including the hydrogen molecule. Up to second order we have calculatedthe symbols of an asymptotic parametrix of the nonrelativisic Hamiltonian ofthe helium atom within the Born-Oppenheimer approximation and provide explicitformulas for the corresponding Green operators which encode the asymptoticbehaviour of the eigenfunctons near an edge.

Explicit Green operators for quantum mechanical Hamiltonians.~II.~ Edge type singularities of the helium atom