Energy from an Approximate Wave Function

IMPROVING THE ENERGY FROM AN APPROXIMATE WAVE FUNCTION 

A simple example is provided by a hydrogen atom in a weak electric field. The chemical potential is given by p, that of an unperturbed H atom, plus Fz, where F is the strength of the field along the z axis. The regions C and D correspond to —z and +z. For any two points, (/zd — Tc) = ( p — zc) - 

To obtain the energy lowering due to charge transfer in Equation (3.35), we find the averages 

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