F-spin mixing andM1 properties of the low-lying states in the neutron-proton interacting boson model

Abstract

The F-spin mixing and M1 properties of the low-lying bands in the neutron-proton interacting boson model (IBM-2) are studied. Application of the intrinsic state formalism in the leading order in 1/N and of the perturbative approach makes it possible to obtain analytical expressions in which a dependence on F-spin breaking terms is clearly exhibited. A simple explanation of many features observed in numerical studies is given. Comparison between the IBM-2 results and the treatment of M1 properties with the extended M1 operator in the IBM-1 approach is discussed. PACS number(s): 21.10. Ky, 21.60.Ev, 21.60.Fw, 23.20.Js