“…In this method, a complex coordinate scaling is introduced to rotate the continuum into the complex energy plane and the wave functions of resonant states, but not scattering states, are transformed into square-integrable functions [10]. Although it involves the solution of a complex eigenvalue problem which causes some difficulties in practice, the CSM has been widely and successfully used to study resonances in atomic and molecular systems [11,12,13] and atomic nuclei [9,10,14,15,16]. The analytical continuation in the coupling constant (ACCC) approach is based on an intuitive idea that a resonant state can be lowered to be bound when the potential becomes more attractive or equivalently the coupling constant stronger, thus a resonant state being related to a series of bound states via an analytical continuation in the coupling constant [17,18,19].…”