2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/84490We show that for a general system of N s-wave point scatterers, there are always N eigenmodes. These eigenmodes or eigenchannels play the same role as spherical harmonics for a spherically symmetric target--they give a phase shift only. In other words, the T matrix of the system is of rank N and the eigenmodes are eigenvectors corresponding to non-0 eigenvalues of the T matrix. The eigenmode expansion approach can give insight to the total scattering cross section; the position, width, and superradiant or subradiant nature of resonance peaks; the unsymmetric Fano lineshape of sharp proximity resonance peaks based on the high energy tail of a broad band; and other properties. Off-resonant eigenmodes for identical proximate scatterers are approximately angular momentum eigenstates.Accepted by PRA. Research is underway currently to apply this method to superradianceAtomic PhysicsQuantum Physicstext