Non-Hermitian effective Hamiltonian and continuum shell model

The intrinsic dynamics of a system with open decay channels is described by a non-Hermitian effective Hamiltonian which at the same time allows one to find the external dynamics---reaction cross sections. We discuss ways of incorporating this approach into the shell model context. The approach is capable of describing a multitude of phenomena in a unified way combining physics of structure and reactions. Self-consistency of calculations for a chain of nuclides and threshold energy dependence of the continuum coupling are crucial for the description of loosely bound states. Schematic and realistic examples of open many-body systems where internal configuration mixing is generated by pairing are presented.