M1transitions between low-lying levels inXe128and the proton-neutron interacting boson model

Abstract
The branching ratios of the collective levels in Xe128 were discussed in the framework of the proton-neutron interacting boson model . It is shown that the experiment is only consistent with rather small M1 admixtures among the low-lying collective levels. These small M1 matrix elements imply strong constraints on the proton-neutron interacting boson model Hamiltonian.