Invariant imbedding and full collision matrix methods: Incorporation of closed channels, complex potentials, and determination of bound state energies

We demonstrate the relationship between the full collision matrix [J. Chem. Phys. 88, 2309 (1988)] and the invariant imbedding [J. Chem. Phys. 77, 1942 (1982)] methods for quantum scattering. We show how to include closed channels into scattering calculations employing these methods, yet retaining the inherent stability of the methods. We develop techniques for using these methods for (single and) multichannel bound state problems to determine the bound state energy eigenvalues. The method is generalized to include complex potentials in order to simulate decay.