Boson mapping in systems with non-degenerate shells

A new boson mapping, which has some aspects similar to the OAI mapping and can be applied also to a non-degenerate system, is presented in order to give a microscopic foundation of the interacting boson model. Numerical calculations of the E2 operator in a two-j system show that this mapping gives a good approximation for the seniority-changing part, and that it stays at least within the accuracy of the OAI mapping, even for the seniority-conserving part. (orig.)