Population of mixed-symmetry states via α transfer reactions

Within the neutron-proton interacting boson model we study the population of mixed-symmetry states via α transfer processes. Closed expressions are deduced in the case of the limiting U_π+ν(5) and SU_π+ν(3). We find that the population of the lowest mixed-symmetry 2⁺ state, vanishing along the N_π=N_ν line, depends on the number of active bosons and is normally smaller than that of the lowest full symmetric 2⁺ state. In particular, for deformed nuclei where the number of bosons is normally large, the relative population of the mixed-symmetry 2⁺ state is of the order of a few percent. More favorable cases can be found near shell closures, as in the case of α transfer leading to ¹⁴⁰Ba.