The finite size effect on resonance poles

The effect of the finite size of an array of scatterers on the position of the resonance poles of the scattered amplitudes is studied. This effect must be studied because in reality, an infinite array cannot be realized. In particular, it is expected that for a finite array of scatterers, the imaginary parts of the resonance poles (resonance widths) cannot vanish as is the case for an infinite double array admitting bound states in the radiation continuum.