In coupled-channel models the poles of the scattering S-matrix are located on different Riemann sheets. Physical observables are affected mainly by poles closest to the physical region but sometimes shadow poles have considerable effect, too. The pur
pose of this paper is to show that in coupled-channel problem all poles of the S-matrix can be calculated with properly constructed complex-energy basis. The Berggren basis is used for expanding the coupled-channel solutions. The location of the poles of the S-matrix were calculated and compared with an exactly solvable coupled-channel problem: the one with the Cox potential. We show that with appropriately chosen Berggren basis poles of the S-matrix including the shadow ones can be determined.
Two methods the complex energy shell model (CXSM) and the complex scaling (CS) approach were used for calculating isobaric analog resonances (IAR) in the Lane model. The IAR parameters calculated by the CXSM and the CS methods were checked against th
e parameters extracted from the direct numerical solution of the coupled channel Lane equations (CC). The agreement with the CC results was generally better than 1 keV for both methods and for each partial waves concerned. Similarities and differences of the CXSM and the CS methods are discussed. CXSM offers a direct way to study the configurations of the IAR wave function in contrast to the CS method.
