[en] It is shown that in the potential scattering for the one-dimensional Hamiltonian the quasi-stationary-state energy can be found as one into which the discrete eigenvalue of some initial Hamiltonian turns under the perturbation leading to tunnelling. The asymptotic properties of the quasi-stationary-state complex energy is defined, which shows in particular that the decay through tunnelling can be interpreted as the transition from the discrete eigenstate to the scattering state of ''not initial'' but of another channel Hamiltonian