EFFICIENT DIRECT CALCULATION OF COMPLEX RESONANCE (SIEGERT) ENERGIES

An improved version of the Siegert method to calculate resonance state parameters directly is presented. A prediagonalization of the Hamiltonian in a real L2 basis and an equation partitioning technique are utilized along with an inverse iteration method (combined with a rational fraction root search) to find accurate positions and widths of narrow resonances. Model calculations suggest that the present method is efficient and accurate especially for narrow resonances regardless of the potential range. © 1995 The American Physical Society.