Inclusion of neutron-proton phonons in the quasiparticle-phonon nuclear model

It is shown how operators of neutron-proton phonons can be introduced into the mathematical formalism of the quasiparticle-phonon nuclear model. The Hamiltonian of the model is transformed by means of solutions of the secular equations for the single-phonon states. A system of basic equations is obtained in general form and a transition made to a system of approximate equations. They are intended for the description of the fragmentation of the neutron-proton phonons and thus for the calculation of the characteristics of charge-exchange giant resonances in spherical nuclei.