Wannier theory for doubly excited resonances

Wannier continuum wavefunctions for two electrons near a positive ion core for energies immediately below the double escape threshold are obtained. Continuation of these functions across the classical turning line imposes a set of constraints. Solutions consistent with these constraints are shown to exist at discrete energies. These solutions represent a series of autoionising Rydberg levels converging to the double escape threshold. The energy dependence of the wavefunction normalisation is derived.