In atomic physics , close coupling is a quantum mechanics method to calculate the multi-electronic atomic and molecular structure from fine structure to hyperfine structure levels and dynamic processes including photoionization ,[ 1] [ 2] collisional excitation and ionization as well as autoionization and their inverse processes. In this method, the multi-electron systems are treated as a loosely interacting electron with a target ionic or neutral atomic as well as molecular, in which the electrons are strongly interactive with each other. The interactive atomic or molecular complex system is reduced into a so-called (N+1) problem. Based on this scheme, the inter-channel interaction, that is, configuration interactions (CI) are involved.
Integrated with other techniques, especially the matrix techniques and multi-channel quantum defect theory, close-coupling method could provide precise structural and dynamical studies of atomic and molecular systems.
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