A multi-shell extension of the interacting boson model

A multi-shell extension of the simplest formulation of the interacting boson model that appends parity-conserving (2) energy excitations to the non-extended theory is proffered. From a physical perspective this extension links the system's low-lying configurations to higher-lying multiple one-particle-one-hole (1p-1h) excitation modes that are in part tethered to the system's isoscalar giant monopole and quadrupole resonances. An application of the theory to low-lying energy levels and known B(E0) and B(E2) values of Sm-152 shows that the results obtained with the extension are better than those without the extension.