Second order concentration near the binding energy of the helium schrodinger operator

Let the unperturbed operator be the helium-Schrodinger operator and let the perturbation be the homogeneous-electric-field operator. It is shown that the first two formal perturbation equations corresponding to the smallest unperturbed eigenvalue do admit solutions in the appropriate Hilbert space. According to general considerations this implies that for this perturbation problem, the phenomenon of spectral concentration holds.