Scaling behaviour of the transmission poles for Dirac comb

The transmission poles of $N$ number of identical Dirac delta potentials placed periodically in one-dimension are examined in the complex-energy plane. The numerical results show that the imaginary part of the poles scales with 1/N. An approximate form of the poles is derived which supports the scaling behaviour of the poles found numerically. It is shown that the imaginary part of the poles are proportional to their real part for the poles close to the ends of the bands.