Three-channel interference interpretation of Fano profile

Abstract Fano resonance is a ubiquitous phenomenon, and it is commonly interpreted as a two-channel interference of the discrete and continuous channels. The present work investigates the Fano profile from a perspective of the temporal evolution of the wave function. By exciting the atom with a δ pulse and calculating the evolution of the wave function, the Fano formula is deduced. The present results clearly show that the Fano resonance is a result of a three-channel interference, which is different from the traditional understanding. The three channels are revealed as the “ground-continuum”, “ground-discrete-continuum” and a previously unmentioned third channel, “ground-continuum-discrete-continuum”. The present three-channel interpretation can be easily generalized to other physical systems, contributing to a deeper understanding of the Fano profile.