M1 selection rules in the neutron-proton interacting boson model

Abstract
It is shown that vanishing M1 transitions between low-lying collective states are not necessarily due to selection rules based on F-spin symmetry, but may also be related to other symmetries of the neutron-proton interacting boson model Hamiltonian. This argument is illustrated for O(6)-like and SU(3)-like Hamiltonians.