Identifying resonance structures in a scattering cross section using the N3+ + H → NH3+ → N2+ + H+ reaction as an example

Abstract

The many-channel partial wave S-matrix is shown to have a meromorphic continuation into the fourth quadrant of the complex momentum plane. This allows one to expand this S-matrix in terms of its poles, inside a contour, and an integral along this contour. The contribution of a resonance is defined in terms of the corresponding residue. A reduced partial wave S-matrix as well as a reduced partial wave cross section are defined and used to identify if a given structure in a cross section can be associated with an S-matrix pole. The theory presented contains both short-range and Coulomb interactions. The formalism is applied to a realistic two-channel model of a charge transfer process.