DOES AN EFFECTIVE TRANSITION OPERATOR HAVE A TWO-BODY PART?(Molecular structure in medium-weight and heavy nuclei)

Abstract

Effective electromagnetic transition operators pertinent to the model space in the shell model are formulated within the framework of the first-order perturbation theory. The correlated operators thus obtained consist of one-body and two-body transition operators, the former of which is considered to be origin of effective charges, while the latter of which cannot be incorporated into the idea of effective charges. Two-body parts of the effective operators which arise theoretically are examined carefully by making the calculation of Cλ form factors of electron scattering as well as the Eλ transition rates. It is shown that the E4, E6 and M5 transitions in the 1f_<7/2> shell nuclei, which have required anomalous effective charges to reproduce experiment, can be interpreted by using the effective transition operators, in which the two-body contributions are considerably large to such an extent that the concept of effective charge is broken down.