The complex stabilization method: Application to atomic resonances

The complex stabilization method is used to compute the position and width of the (1s 2s 2 ) 2 S He − resonance using a number of different basis sets. All of the results converge to the same eigenvalue we obtained earlier in a so‐called complex coordinate calculation. This calculation uses the unrotated real Hamiltonian with a square‐integrable basis without explicitly imposing any boundary condition. Calculations are reported in which the bases contained one and two complex basis functions. It is shown that the resonant eigenvalue is easily distinguished from all other eigenvalues.