Quasiparticle-phonon equations of motion are solved starting from a microscopic realistic many-body Hamiltonian. In this microscopic quasiparticle-phonon model (MQPM) the relevant part of the three-quasiparticle Hilbert space may possibly be taken into account even in calculations using large single-particle bases. As an example, the MQPM is applied to the calculation of energy levels and Fermi and Gamow-Teller beta-decay transition amplitudes for transitions between odd-mass ${}^{127-133}\mathrm{Xe}$, ${}^{127-133}\mathrm{I}$, and ${}^{127-133}\mathrm{Cs}$ isotopes. Considering the fully microscopic nature of the MQPM, comparison of its results and data indicates a rather satisfactory agreement between theory and experiment.

• Received 18 August 1997

DOI:https://doi.org/10.1103/PhysRevC.57.1237