Photoionization properties of an atom with two autoionizing states

We have investigated the photoionization properties of an atom with a ladder coupling scheme involving two autoionizing states coupled to each other.The effects of the coherent coupling between two autoionizing states and between the low-lying autoionizing state and the continuum on the ionization yield are discussed.The conditions leading to atomic coherent population trapping and the coherent population trapping states are given explicitly.