Slow electron elastic scattering by a target represented by different zero-range potentials

The general formulas to calculate the phase shifts of wave function of a particle scattering on a target formed by a pair of non-identical zero-range potentials are derived. It is shown that at asymptotically great distances from the target the continuum wave function of particle is presented as an expansion in a set of other than spherical, orthonormal functions. General formulas for these functions are obtained. The special features of the S-matrix method for the case of arbitrary non-spherical potentials are discussed.